What Causes A Cut In The Vaginal Opening?

I m a teenager and have never done anything sexual. For about six months now I ve had a cut about 1cm to the right of my vaginal opening. At first it was small and hurt only a little, so I kept it clean and left it alone. I remember that it was slightly itchy. However it never went away and its simply grown, its now around 1 and a half inches long and stretches from near the anus up to past the vaginal opening. It sting and it simply won t heal, what is this and what can i do? Its a few mm deep and looks quite raw. I also have a sore crack and around the anus even though i wash thoroughly and wipe clean, and it often bleeds. Help so I can finally heal, I m fed up of these personal areas being like this, especially as I m getting older.