This was asked before on the old board I believe.
If you can afford to do it, get them removed, if you can't you dont have to. But definitely ask an imam.
As a bit of personal advice and having seen awful tatoos, I wouldn't advise getting it covered over with something else unless your sure the result won't be bigger and hideous. Your body after all, you're the one faced with it every day (but I guess that must be one lesson you've already worked out for yourself).