please help

today, my boyfriend and i had sex and when he thrusted into me at one point, it hurt for a split second and when we looked down a few minutes later as we were changing position we noticed a blood and quite a lot of it. i don't know what's happened but i put a mirror down there so i could see what had gone on and it looks like there's been a string of tissue or something that's ripped in half. will it heal itself? what do i do?