Hi,
It could be an ingrown hair if you shave down there, or a sebaceous cyst or maybe even bartholin cyst. These cysts are common and most of the time do not have to be drained, but if it is uncomfortable and painful, then a trip to the doctors may be in order. I've had 2 that have needed to be drained and it only took a couple minutes at the doctor and it brought instant relief. Since you've never had intercourse I'd say there's not a huge worry there for an STD, not does it sound like an STD by what you describe. Good luck :)