Pan sometimes chews at his feet too. We noticed small bumps between his toes, and in a few days his feet hurt him so much he could barely walk. And it happened so fast!
When I took him to the vet they did a scrap test and he has bacteria growing in between his toes. So they prescribed Cephalexin for the bacteria and a steroid, Prednisolone, to help him feel better. But even though his feet are better now, they are still really rough so every night I slather his paws with utter cream and put booties on him.
I'm not sure about what to put on an open wound. I would suggest at minimum cleaning them the best you can and wrapping them up to prevent infection. Also, pull out the trusty e-collar to prevent him from causing anymore damage.
But if his feet are bothering him enough for him to self-mutilate, I think a trip to the vet may be in order.
In my experience a yeast infection will have a really bad odor.