Too rough??

So last night my boyfriend and I had sex as usual, but it was a bit more rough considering the fact that we didn't have to be quiet. Toward the end of the 3rd round I noticed there was a bit of cramping pain and swelling around the opening of my vagina at the bottoms of my labia the swelling and pain went away after a few minutes but I was wondering if anyone knew why this happens? It wasn't from friction because it was beneath the skin.  It's never really happened before and we've been a lot more rough than we were last night.