Should I be concerned?

For the last few weeks,my right knew has been getting stick when coming out of a resting position. I can hear it crack, and feel it crack during certain movements as well. I’m a runner, and I lift. Today, I just noticed what looks like purplish rings forming with white in the middle close to the area where the pain has been. The rings feel swollen but don’t hurt to the touch. What can cause this?