During sept in a field hockey game the ball was driven into my ankle and it swelled and bruised. now it is still a bruised and swollen but why?

Be seen: If you are still having significant pain and swelling for months after an injury to your ankle, I would recommend you be seen and examined for an accurate diagnosis. The most likely thing we will see with that mechanism is a contusion in the bone, but these are usually pretty much resolved by 8-12 weeks at the most. There may be a more serious component to your injury.