I agree with the above comments, its most likely because he pushed against your cervix too hard. But if this is a pain you feel while not having sex you might consider having it checked out.
it is normal.. the only problem is u might not have been ready and he penetrated too deep.. or you people had a bit of rough sex.. take care the next time...rest there's nothing to worry... it's a thing to enjoy so relax urself at that moment and tell him if u r uncomfortable... good luck..
It could be that he penetrated you too deeply, if he has a large size penis, and you are small (sometimes it doesnt matter if you are small or big) and he penetrates deeply and roughly, especially when you are not ready to recieve him fully, that causes pain..