Vaginas health question.

I had unprotected sex 2 weeks ago (not the first time I do since my partner and I are exclusive for years) and took the after pill soon after and a week later I started my period and it was heavy as hell. But when it ended I noticed a big lump like pimple in my vagina and it hurts when I try to pop it and it won't. Are pimples down there normal or is it something I should be worried about or could be a side effect from the pill?