These are awful to get to heal--Patrick has 2, 1 was from a cyst removal and was left to heal open, 1 tear that we had stiched.
What you want to do is put a bunch of neosporin in there, and gently wrap it with some gauze then vet wrap, top with a baby sock. Try some bitter apple if you need it to keep him from licking. If that doesn't work, I don't know the breed, but is a bite-not collar possible?