You might consider
giving him a nutritional supplement called "MSM". You can buy it at healthfood stores or Walmart and it is great for helping get rid of toxins and promotes healing. We had a lady here in Florida that noticed her dog had been (she thought stung) on the nose and it's nose was swolllen, so she rubbed some lotion with MSM in it on the dogs nose. Over the weekend her dog did better, but on Monday she took him to the Vet to get things checked out. The Vet told her that her dog had been snake bit and as best he could tell it was multiple strikes by a rattler, he also credited the MSM with saving her dog's life.
We had a stray cat several years ago that we rescued, he was tore up by raccoons and almost dead. One of his front legs looked like a chicken drumstick that had a huge bite taken out of it. The Vet said he could patch him up and that he would live, but that he'd never regain use of that leg or paw. We fed him MSM and rubbed lotions with it on his wounds just tring to get the wounds to close up and healo, Over time we noticed the wounds not only healed, but the muscle, skin, and even his hair grew back, after several weeks you couldn't tell he had ever been hurt.
PS: It's great for people also :O)
"Fly-fishing has many attributes, but none more pleasing than it's ability to liberate the young boy that still hides within me and to let that boy live again without embarrassment or regret, sorrow or anguish." Harry Middleton