Umm. well it didn't hurt me at all. Reasons it would hurt would be breaking of the shoot . I've forgotten the name. anyway - there's a little membrane that get broken. I think this can be thicker or thinner in some girls. Not all girls have it when they decided to have intercourse too. Personally, I'm pretty sure mine broke in gym class in grade 5 (exercise can do that so can tampons, fingering.). Could also hurt if you are tense or if you aren't aroused enough/ or just haven't produced enough lubricating fluid.
Like someone else said before watch out of "hitting the top" ie/ cervix. That can hurt or feel good to some women- but I think it'd be best to steer clear for the first few times till you figure out what's going on.
If you haven't gone through the process of manual stimulation/ fingering with your significant other, I would definately do that first. My relationship at your age was the one I lost my virginity in and we were messing around for oh a good year before I decided I was ready for more. That way we were both really comfortable with each other already. Not that you need to wait for as long as did - or wait less. It's all about when you feel okay with it.