Do I have an internal bruise?!

I am 15 years old and about 2 months ago I was snowboarding and crashed pretty hard. My knee automatically hurt very bad and got very hot. It hurt to keep my leg bent for a period of time then straighten it. I had a bruise for maybe one week ish and then it went away. I thought everything was fine until I randomly get sharp stinging pains on the knee or if i lightly bump it on something the stinging pain comes back and the pain does hurt a lot but goes away within a minute. I have been trying to figure out what is wrong with it. Any suggestions or ideas would be appreciated.