Charles, I had one come up on a gyp about 10 years ago that sound like what you have. I never took her to the vet and just stopped running her for a month or so. The knot finally busted and a few days later, she was dead. She was a 12-15 months old. If it is soft, I would draw 1 cc of dex and 1 cc penicillan in the same needle and inject the knott. 2 cents worth from just a good old boy, not a pro. If the dog is young, I think it may be a problem. If older, could just be a cyst.