I Have A Small Pea Size Lump That Moves When

I have a small pea size lump that moves when pressed, on the top of my left knee on the right side. This has been there since May, when I landed on it at basketball and it was really sore for a few months, but now the pain has gone (comes occasionally when pressed or leaned on) and I have a small lump?

Any idea on what this is?

Thanks