What Causes Bump Near Vaginal Opening After Having Sex?

Hi, the last time I had sex was about 2 months ago without the use of a condom with a guy who had slept with a lot of other girls (i have never had sex with anyone else). Today I noticed a small, soft bump near the opening of my vagina but sort of on my bum. It is the same color as the skin surrounding it. Should I be worried? It doesn't itch, pus, or hurt.