Not sure what is wrong with my knee...does anyone have any input?

I had a problem with my knee a few years ago when I was running. The doctor said that my kneecap is straight and should be crooked...I had to go to physical therapy to strengthen the muscles that tilt the kneecap. I recently took up running again...and have a similar pain so I figured that I would just need to work those muscles again. But today I noticed a hard lump (feels almost like the bone) that sticks out on my knee just below where the kneecap ends while the leg is straight. It doesn't hurt to touch but my knee does hurt a little to run on it. Any ideas what this could be?