How To Treat A Growing And Painful Scab?

I have a scab which begun as a pinpoint wound like an insect bite with redness which has since grown to about the size of a dime with a clear scab over the wound and redness and swelling about the size of a quarter (one euro). About a week ago it started leaking a brownish fluid. About four days ago it started to be painful when it would get touched, even if by the cloth of my pants. The redness around it is somewhat hard like a callous. I am worried it is a spider bite and might keep growing.