I would find a vet with an Infrared Cold laser and spend a little money on it, it's usually around $25 a treatment but well worth it, it should only need 1-2 treatments. My dog had a bad one from an ice cut that he ended up licking and made a bad granuloma on his foot, went the whole route with steroids and antibiotics and foot bandages, my vet friend did one treatment on it, we wrapped it back up and the next day it was gone and I was able to run him in a hunt test. The only think I would add to the treatment afterwards it apply raw honey to the granuloma and rebandage it overnight.
I have my own laser now, just used it on a burn from an exhaust pipe on my husbands arm, it had blistered, today no pain and the blisters are gone and it's already healed remarkably in one day.