Is Aching Pain In Knee With Lump Above The Knee Concerning?

I am a 19 year old female. I noticed a lump right above my knee about 3 weeks ago. It is not visible but you can feel it below the skin, about as big around as a golf ball. I have tried ice and hot towels to make it go down but nothing works. It is not painful to touch but I do occasionally get an aching pain in my knee. What could this be? Is this something I should worry about or will it go away on its own with more time? Thanks!