SO too hard??

Two days ago my SO came over and we were super horny and I was grinding on him but his dick was really hard. Like I had to position it a certain way so it wouldn't hurt. The next day he came over again and he got on top and it really hurt. That night I looked at it and the skin outside of my vagina is red and hurts to touch. Today it's not as red but hurts still. What should I do?