Knee lump

This morning I woke up with a golf ball sized lump in my knee cap. My knees regularly have small bulges but my left this morning was 5x the size of my right knee cap.. What could this be from? Should I just wait it out or go to the doctor? There is not really any pain. Every once in a while it will ache for a few seconds and than stop. I didn't hit it on anything either 😕