Hello. I'm sorry you've injured your knee. It's difficult to say what's going on here without an examination. If you fell directly to your kneecap, you might have
prepatellar bursitis (inflammation of the bursa overlying the kneecap). This should eventually calm down with ice, rest, and anti-inflammatory medications (
ibuprofen,
naproxen, etc.). A patellar brace (a
neoprene sleeve with a hole cut for your kneecap) might also help.
If you twisted your knee as you fell, you might have a more serious injury, such as a meniscal tear, a torn or stretched
cruciate ligament, or a strained collateral ligament. These injuries take longer to heal, and in some cases won't heal without surgery. Ice, rest, and anti-inflammatories should still help, though.
To confirm your diagnosis and determine the best treatment for your knee, you should really see a physician for an evaluation.
I hope that helps, and I hope you're back to playing soccer soon!