swollen labia minora

I noticed after my menstural cycle ended, yesterday, that the right side of my labia minora (at least that's what I am assuming it is) is swollen...there's no pain, and it is not itchy. I thought it was a blister, until I sat down and actually tried looking at it was a mirror, and it seems as though it should be there because it has it's other half on the left side, which is why I say it is my labia minora. I just wanted to know why it is swollen, it can't be from sex because I noticed it after my period ended, and my boyfriend and I do not have sex while I'm on my period. Could it be from the tampons I was using?? Allergic reation??