sebaceous oil gland causing problem

My senior cat, Spooky, had a bump on his spine.  It would break open and be kind of a nasty looking little sore and then heal up, then start the whole process over again.  The vet said it is a sebaceous oil gland and put him on a week of antibiotics.  She said if that didn't work, he might need a minor surgery for it.  The antibiotics did not work and we are back to square one.  Ointment has not helped either.  Does anyone have any experience with this or ideas about what I could try at home?  Thanks.

P.S.  The vet did not seem overly concerned about this and it does not seem to be bothering Spooky at all.

It could be a cyst.  I get them occasionally as did my father, in humans it's a genetic thing.  Mine will get inflamed, open and drain.  Eventually they come back, I have 2.  The only way to get rid of them permanently at least in people is to surgically remove them so that the complete cyst is gone rather than just emptying.