Hello, I Have Question About A Bump At The Very

Hello, I have question about a bump at the very top of my thigh. Basically, it's on my panty line. It is under the skin, it has no head or anything to pop. Its like a ball underneath my skin. It is very painful probably because every time i walk it rubs. I have some bactroban cream left over from something else a while back and i was wondering if that was okay to put on it. I've actually had this problem before and it's always in the same spot, it never goes away fully its normally just a tiny dot like a scar. Every now and then it comes back but it usually goes away within a couple days. This time it seems more irritated and doesn't want to heal. It's about the size of a marble underneath my skin. An ER doctor i went to a couple years ago for the same thing, says he thinks its a sebaceous cyst.