Suggest Treatment For Painful Knot On Upper Side Of Buttock

I have a golfball size hard knot on upper right side of buttock almost inside crease...It hurts so bad I can not sit straight up on buttocks. I thought something had bit me because the area started itching so I stratched area, then mashed it a little...with in two days it's grown to golf ball size and very hard...doesn't seem to have a head...doesn't appear to be a boil nor a spider bite...Other small appearing pimples around the area...do you have any suggestions as to what this may be? I am in lots of pain...feels like it has fever in it..has a stinging burning sensation today...It actually hurts to walk. Please help, for I can not drive to a Dr office due to the pain if I try sitting on it.