He needs to go to the vet. Was at the vet about 5 years ago and a horse had been bitten on a hind leg. He looked horrible. Vet was telling me he was a son of Reminic. He was so poor I just could not imagine people not taking care of their horse. He had lost that weight in a matter of days because he was in such pain. His back foot had curled up and he could no longer straighten it out. Also with animals if not treated the snake bite will cause the to get skin abscesses in more than one place. Again, horse needs to go to the vet.
They usually recommend an anti inflammitory. Maybe even antibiotics. We've had several bit, always in the face and all survived with no lasting affects except one. I think it fried his mind. He was a real A-hole after that.