HELP PLEASE

Okay so my boyfriend and I had sex last week and something went wrong and it hurt, we laughed it off but that night my vagina was hurting a lot since then every time we have sex I'm sore afterwards which means we can't do it more than once that night because I'm too sore. I considered the STI thing but we were both checked and we aren't sleeping with anyone else but each other (don't bring up cheating please because I don't want to hear it). I know I need to go to the doctors but can anyone help me with what could be wrong? I'm really tender down there and it stings a lot.