HELP!!

Ok. I'm 15, 16 in a month.... and today while i was taking a shower i noticed that my butt felt weird and sort of hurt so i reached down and touched where it hurt and realized there was a bump there.
well so i didnt have to get anyone else involved i grabbed my mirror and held it low enough so i could see what the bump looked like.
its right on the side between my vag. and my anus.
i googled and searched but couldnt find anything to say what it was.

its not red, looks the same as my normal skin except its the size of a big pea and its hard and painful to touch.
its not itchy. it just hurts really bad when i get up and walk around and when i move around while sitting down.

do you think its something to be concerned about and something i should get checked out?
or just something that'll go away soon..

also, any ideas what it might be??

i have a lot of cancer in my family so im pretty freaked out when i get mystery lumps. :[