Start with giving it a penicillin shot.   It's quite likely just a bacterial infection, possibly strep.

Did you farrow the pigs or buy them?   Are they inside or outside?   Anything rough it could have cut itself on?

If they were ours we'd vaccinate for Circo, Myco and PRRS.     If you don't have many pigs around (I suspect you don't) that may all be completely unnecessary. 

There are two types of Myco, the one the vaccine is good for is a respiratory disease, the other one (vaccine does nothing) causes stiffness in the back hips of 80-120 lb pigs.   I really doubt Myco is causing your pigs foot problems.