Dude do you take alot of aspirin or have high blood pressure? If so that could be the cause. Or does your family have a history of that disease that causes you to bleed easy? It could be a fragment of you nose cartilidge(sp) that broke of and is sharp and when you hit the nose inward it starts to bleed. You could also (worst case scenario) have a tumor or a clot. It may also be a cyst. i would have it checked though as repeated bleeding from anywhere is something that needs checking.