I'm 19 years old, 5'4", and 120 lbs. I had a black scab on my calf for about 2 weeks, but I'm not 100% sure what it was from (possibly a bug bite since it was there the morning after I was wandering in the woods near a lake in shorts). It recently formed a 1 in diameter white swollen circle and around that it's all red. It's extremely itchy and the area around the scab is very tender and I'm almost certain that it's infected.