I Have An Insect Bite On The Calf Of My

I have an insect bite on the calf of my leg that's very red, the size of a fifty cents piece with a white sac in the center. The insect must have ceawed up the inside of my pants leg while I was doing yard work on Saturday morning. I swatted as soon as I felt the bite so I didn't clearly see what bit me but I saw what was left of it was brown.