Blister?

I have a tiny bump that looks like a blister on my groin area. I'd rather not post a picture, but it's red with a white center. When pressure is put on it, it hurts a lot. It's been noticable for maybe 2-3 days. Its likely from shaving without using cream. I don't want to tell my stepmother because she'll ask why I've been shaving down there and I don't want to get into that with her. Any clue what it could be, or how I can treat it?

Update: Seriously painful at the touch. Not that I'm trying to touch it. Help! What is this?! I'm sure it's not an STD, because my boyfriend used a condom and there's no way he could have an STD anyway.