Suggest Remedy For Painful Boil In Buttock Cheek

Im 32 yrs, female, non smoker. 4 days ago i felt what i believed was a boil on my buttcheek. It is very painful. It is about the size of a quarter, very swollen, it feels like a boil but i used black sab on it for 2 1/2 days and it hasnt done anything as of yet. I tried to burst it althought its in the worse place so i can only reach 1 hand to touch it, nothing has come out but a little blood, i tried it again a day later and a tiny bit of pus came out but just on the tiny scab that is covering this thing. Alls i can say is that it is day 4 and this thing is very painful. I started to use bacitracin ointment last night, i havent felt a difference. Right now i am trying to figure out if this is a spider bite or a cyst..i may have to make a trip to the emergency room. What would your advice be. Thanks! Theresa.