Someone please help!

I have like loose skin hanging on the the left side of my vagina. Inbetween my labia major and minor. I say it's loose extra skin because the other side does not have the same thing. Last Night after having sex the loose skin swelled up enormously. almost looking like a enlarged blister. It didnt seem liquid filled and does not itch at all. it just looked like a boil or blister about the size of spoon(without the handle) it went back down to it's normal loose skin the next morning. does anyone have any explaination for this?