What Should I Do About A Hard, Bruise-like Lump On My Inner Calf Below The Knee, With Ongoing Edema And Osteoarthritis?

I have had edema in my left leg for several weeks (actually off and on for over a year) I have been taking a dieritic for 2 weeks and the swelling has reduced some. However, yesterday I noticed a hard lump that feels like a bruise on my inner calf just below my knee. I have osteoarthritis which is bone on bone and have been having extreme stiffness in this knee for over a year. What should I do about this hard lump? (it is not discolored and I have not bumped or injured myself)