Hello, I have a circular, red spot, about the size of a quarter on the back of my right calf. It itched initially for 3 days, but itching has subsided. It has remained the same size and color for 3 weeks now, but has gotten hard and lumpy around periphery of the spot. I have found no ticks on myself and have not been in contact with any unusual materials. However, I do recall being bitten by mosquitoes on both legs when doing yard work. Any insights would be greatly appreciated.