What Causes Mild Hearing Loss After A Head Injury?

Hello. About 1 1/2 months ago, I hit my head, about 1 inch behind the left ear in the 5 oclock position. Nothing was unusual until About 2 weeks later; I was out with friends and came home after a run. I noticed that my left ear was becoming very quiet at dinner and felt like cotton was very deep in my skull. I was on the hot side Because of my run, I feel like this greatly had something to do with the problem. (No headaches, no soreness, nothing else) I was hoping this problem would go away, but it persists weeks later. Some days I barely notice, other days are worse. I cant tell if this is a muscle problem or if Ive broken something. Any help or insight is greatly appreciated.