There's a bump under my armpit that has been there for a fee weeks, it hasn't grown is that something to worry about?

May be. It could just be an ingrown hair or a skin tag. However, there are glands in the armpit too, and you don't want one of those to be swollen for more than about a week. It could also be a cyst. You probably should get checked out to make sure it isn't anything serious.