Suggest Treatment For A Blister Like Bump On The Labia Majora

Hi I'm a 22 year old female. I'm a virgin. I noticed a blister-like bump on the labia majora where it almost ends (near my upper thigh). It formed during my period about 2 months ago and it never bothered me. It's still there and it keeps shrinking and coming back. Today I tried squeezing it, it just bled a little but no puss or anything. What can it be and how do I treat it?