Finger still swollen 10 months later?

Last August I hurt my left index finger. The pain was there but nothing too substantial. A few days later it started to bruise down the hand so I went to a clinic that had an x-ray. After a brief few questions about how I got it and where the pain was, the doctor informed me that it was a just a sprain. No x-ray was performed, the finger wasn't splinted or set. Whatever, I left the clinic. 10 months later the finger has full flexibility and no pain or bruising but oddly, halfway down the finger it is still swollen. What is wrong with it?