Vaginal cyst?

There is a slightly smaller than pea size bump on the inside of my vulva (I think that is what it is called). It is hard and is the same color as the rest of my skin down there. It only hurt if I squeeze it, it also turns white when I squeeze it. I haven't been sexually active for about a month and a half, but I have been masturbating. And it did come up the next afternoon after I had masturbated the night before and I didnt clean up the area afterwards. So could it be a vaginal cyst or a boil? Or is it something worse like and std or sti? Because I havent had any other symptoms of than my discharge from ovulating turning from an off color white to a very pale yellow? Please help I'm getting really freaked out and I can't go to the doctor because my mother hasn't let me go for four years. And I'm 18 but she still has my insurance card and won't let me have it plus I don't have a job so I can't afford a doctors visits out of pocket.