Yeah, I agree with mama_t. You don't want to get an infection, and it's always good to just be sure. I don't know how common it is to tear from sex, I personally have never experienced it. Remember this: when you're having sex you need to be honest and open with your partner, and if it hurts or you're uncomfortable, he needs to know. Upon entering a girls vagina, the guy needs to be gentle and work it in slowly, not just ram it in! The skin of the vagina is very delicate and sensitive. Natural lubricant or lubricant form a bottle is important during intercourse so that irritation and chaffing doesn't occur.
The tearz are probably caused from the rough sex. The pain is them trying to heal but if its so painful I would go to the doctor to make sure they arent infected.