Strange lump :/ need advice on what to do :/?

ok its a bit personal this question :( but i sort of noticed a strange small lump on my 'bum hole' as such, at closer inspection it seems to be like a vain or something, i'm not sure, it looks like a vain as it is blue, it seems to have swelled up a bit, its only tiny, no bigger than a pea, its only been there recently, its not uncomfortable or anything, its just weird that its there, i really have no idea what to do :( I'm 15, and don't know whether its anything to be worried about or not, please someone help :( :(