PLEASE HELP!!

I have noticed a pain in my vaginal area the past couple of days. I peeked down there today, and noticed a lump. It's approximately the size of a mosquito bite (though I know those can vary in size...in between a marble and a pea). It's on the base of the inside of the left flap of my labia (I think that's what it's called?). I've never had sex before so it cannot be a STI. It hurts badly to touch. I am not on my period, but wear panty liners between periods because the discharge annoys me. I am shaved completely. Could it just be because of irritation? I've heard of labial cysts. Is this that? Has anyone had anything like this? Any advice would be greatly appreciated.