The doctor is still an absolute prick for pretending to OP that he would honor that promise, though. If he could not make that promise for malpractice reasons he should not have made it, simple as that. It probably would have been significantly less upsetting for OP that way too.

Yet another reason I'll never get a tattoo. But that still seriously sucks, OP. I don't know if this would be considered malpractice though, so sadly, short of getting another tattoo, I don't know if there's anything you can do.