How Can A Painful Knee Lump Be Treated?

I am 14 years old i weigh 130 pounds and i am 5 ft 8in tall. I have a bump on the side of my knee near the top and it is swollen.. It also hurts behind my knee like on the back of my leg when i walk.. I have been icing it for alittle while but when i walk or try to run it still hurts. I have a softball game tonight so i was wondering if there waws anything i could do to help it not hurt anymore.