A tattoo in a dream often represents permanence -- a decision, belief, or identity you're marking as fixed and unlikely to change. Getting a new tattoo can reflect a form of self-expression you're ready to commit to, while regretting one may point to an old choice that no longer fits who you are.
He that asserts things that can never be proved by experience is deceived and ambitious, but thus it always happens, those that are most ignorant of Art delights to boast of doing things different or wonderful. - Cardan Girolamo (1501-1576)