I have a bump on the back of my leg, it's swole and hurts. red all around, and a little brownish color dot in the middle of it. spider bite? or what?

"Bump": It would help to know exactly where the bump is on the back of your leg. Is it behind the knee? If so it may be a Baker's cyst. On the calf..and we need to think about a clot deep in the veins. Anywhere else and the chances of a spider or insect bite go way up. If so watch for signs of continued infection and see your doctor for further analysis.