My rail-dog "Kathy" had these very bumps! (I know exactly what your talking about)!
The vet said they were caused by an active skin fungus and she (vet lady) gave me a two weeks supply of these antibiotics for her and she cleared right up fast, but you have to complete the entire two week regimend or it'll come back & worse, so complete the regemend! (They were like $32.00 for the pills). I never paid the vet, & she totally understood & never ever billed me, so depending on the vet whether you get away without a bill. (If they really care about animals, they'll do this for you)........
PS......It's a form of mange, but way less destructive and easier to get rid of............but of course there are many types of skin dissorders & this is what "she" had......(Not saying your doggy has this), but just a note.