A man complains of pain and skin redness in his right calf. He has a fever of 38.5°C and enlarged and painful inguinal lymph nodes on the right. The skin of the affected limb is edematous, hyperemic, and has rash elements in the form of vesicles filled with a dark liquid. Its palpation is painful. There is a clear margin between the red area and healthy skin. Make the right diagnosis: