My Legs Have Been Waking Me Up Nightly. They Feel

My legs have been waking me up nightly. They feel achy (not cramps) around the knees and calves. I get the need to either stretch/flex the legs, or, I find bending them tightly to my chest can provide some relief. I have also discovered a small lump in my calf. Any idea of what I am experiencing?
Thank you,
vickie