Suggest Treatment For An Infected Open Wound

Hi im 33yr.old female. I have an open pea sized wound that's bleeding and hurts terribly, its a purplish around the open area. Several days ago I think it was a pimple didn't pay attention to it until today when my pants started rubbing against it. I also have been really cold like having the chills sometimes to the point of shivering. Please help I have no clue what's going on but it doesn't look good!