What Could Be Causing Severe Swelling, Pain, And A Warm, Red Rash On My Right Ankle And Shin?

my right ankle and foot is severely swollen. for a week now. its painful mainly on my shin. there s a red rash like around my leg starting at my ankle and going just below my knee. it has a warm feeling. I went to er and got a test. I tested negative for DVT. what else could it be?