Go to the vet....it might be nothing but then again it may not...its better to go to the professional rather than possibly losing him and having to live with the fact you coulda helped

Well, I would first advise you to clear out his run/cage and maybe do a quick sweep for any sharp objects in there to help to find out how he may have cut himself if you don't already know that. Then spray his run with disinfectant to prevent the risk of further infection, and maybe give him a small bath to cleanse his underbelly of bacteria. Cut his claws too.
Leave him for a couple more days and if the scab grows more swollen or begins to go pussy, then yes you should take him to the vets otherwise there's...

Well, I would first advise you to clear out his run/cage and maybe do a quick sweep for any sharp objects in there to help to find out how he may have cut himself if you don't already know that. Then spray his run with disinfectant to prevent the risk of further infection, and maybe give him a small bath to cleanse his underbelly of bacteria. Cut his claws too.
Leave him for a couple more days and if the scab grows more swollen or begins to go pussy, then yes you should take him to the vets otherwise there's no point in wasting money on something is there.
Hope this helps you and that he gets better.

HAMSTER INJURIES:
Hamster with an injury caused in a fight Despite all our best efforts our little hamsters get hurt. It may be from another hamster or pet or just an overactive sense of adventure. Most injuries to dwarf hamster are caused by other dwarf hamsters. As cute as they may be, they can also be quite vicious when they are angry. The first thing to do after giving the injured hamster proper medical attention is to remove the source of the injury. If the ...

HAMSTER INJURIES:
Hamster with an injury caused in a fight Despite all our best efforts our little hamsters get hurt. It may be from another hamster or pet or just an overactive sense of adventure. Most injuries to dwarf hamster are caused by other dwarf hamsters. As cute as they may be, they can also be quite vicious when they are angry. The first thing to do after giving the injured hamster proper medical attention is to remove the source of the injury. If the injury was caused by another hamsters, do not allow the hamsters to continue living together in the hopes that their relationship will improve. If one of the hamsters is already hurt the tension between the hamsters will escalate rather than dissipate.
Small injuries can be taken care of with topical ointments. Make sure to check with a veterinarian however ot make sure that the ointment you wish to use is safe for hamsters. If you harmster's injury is more serious you should contact a vet immeidately.
Hamsters are resilient little creatures, and if given proper care, should be up and playing again very soon.

COMMON INJURIES:
ABSCESSES:
Hamster with a nasty abscess Usually the result of cuts and bites that have either been overlooked or haven't been properly cleaned. Once an abscess (a lump filled with fluid) has developed, a trip to the vet is required. The verterinarian will likely lance the abscess and then drain it. After the procedure the veterinarian will probably prescribe antibiotics for a time while the wound heals.

BROKEN LIMBS:
Normally the result of a fall. If a broken limb is suspected it is best to obtain the advice of a veterinarian who probably will NOT wrap or splint the break since it will only be a matter of time before it is chewed off by the hamster. The limb may not heal straight but this won't likely affect the resilient little hamster. However, if the limb is being dragged around or it looks to be inflamed, vet assistance should once again be sought. To allow healing time without additional injury, the hamster should be moved to an aquarium (no barred cage as the hamster might try and climb), the wheel should be removed and any other toys that would require the use of the broken limb. Keep the little one as quiet as possible and let the broken limb heal naturally.
CUTS AND BITES:
Young pups sometimes get a little overzealous in their squabbles, and sometimes fights may break out as the result of an unsuccessful mating attempt thus potentially causing cuts and bites. The injured hamster with just minor cuts and bites should be placed in a separate cage. They will then lick and clean the cuts and bites, which should heal quite quickly. More serious cuts and bites should be tended to by cutting the hair from around the would with blunt scissors. To prevent the cut hair from falling into the wound, wet the scissors and the hair will cling to the scissor blades. Once the hair has been removed, was the area with a saline solution or peroxide and coat with a good antibiotic ointment. Veterinary treatment should be obtained at the first signs of infection or the start of an abscess.

OMG!!!! My Guinea pig had a similar thing he had like an open cut on his leg an his leg was very swollen i never did anything and thought he would heal but it never did, the worst part was is he later got an infection which KILLED him I think you should take him to a vet ASAP please although vets rarely take in small mammals so check with them first. The scab could be cause by lack of firm padding i am not sure ,you should get the vet's advice and clean his cage but what i am sure is he needs a vet you could try to clea...

OMG!!!! My Guinea pig had a similar thing he had like an open cut on his leg an his leg was very swollen i never did anything and thought he would heal but it never did, the worst part was is he later got an infection which KILLED him I think you should take him to a vet ASAP please although vets rarely take in small mammals so check with them first. The scab could be cause by lack of firm padding i am not sure ,you should get the vet's advice and clean his cage but what i am sure is he needs a vet you could try to clean his wound with anticeptic fluids.I hope he gets well

P.S what's his name my guinea pig's name was patchie because of a patch in his eye and partly because he was adopted and already named :D