I Fell And Hurt My Elbow Outside, At First I

I fell and hurt my elbow outside, at first i thought it was just a bruised bone. I noticed about a weeks after the fall that i was still in pain and there was a dent in it, the dent is small on the tip of my left elbow. So what could have happened to my elbow, it does not hurt that much i can bend it but when pressure is put on it it hurts.