Hi cassie,
as everyone here keeps recommending to anyone asking about stuff like that: have it checked out! It isn't necessarily anything, but the longer you wait, the worse it will get if it is something. And if you're worried about the cost of the doctor, it will only get more expensive. This is not the right place to save money.
Personally, i'm battling hodgkin's lymphoma, which was diagnosed from a lump above my collar bone, so I know what i'm talking about. But i've had other lumps that haven't been anything, so don't get too worried. Just check it out and you'll sleep better.
All the best.