What Causes Painful Red Bumps On The Lower Legs?

I developed painful red areas and bumps on both legs below the knee. I saw a dermatologist who gave me a steroidal cream. I few days later I saw a doctor at an urgent care center since it was getting worse, and I developed major swelling in both ankles. They diagnosed me with Cellulitis. They have me 7 days of Keflex, which I just finished. As the swelling went down, I noticed several painful bumps - some in red areas, and some where the skin was not red. Definitely I have improved, but I am not all better. The largest bump (which I thought was from bumping into something 2-3 weeks ago) is still there. I am diabetic, but have not had any major complications associated with it. Should I see an internist, primary care or go back to an urgent care center? Should I be very concerned?