It depends how bad it is, but usually only a few days if its not very bad or maybe a two weeks if its quite bad . Id be surprised if it was much longer than that.
How long does it take a bruise to heal?
On july 3rd I fell into a baseball bat and it bruised my face really bad and its still there over two months later. It faded a lot but you can still see it
Rub it a little every day. That will help.
Next time put pressure on the area right away and hold it for 2 or 3 minutes