TMI warning -- Advice needed

So.. my boyfriend and I recently had sex and everything was fine. Now, two days later, we were attempting to do it again but for some reason I couldn't. I don't know why? The easiest way to describe it is it basically burned and stung when just the tip was put in. this has happened before but usually after one round and we'd try to go again & I couldn't get wet again. but this was two days later, and now on the third day it still hurts just sitting here. does anyone else have this happen or know why????