Spider bite. How long to heal?

I got bit by what I ume was a brown recluse. Before you ask, no, I did not go to the doctor. My pharmacist recommended putting prid, a drawing salve on it. It never got worse, per se. It is no bigger than an average pencil eraser. A little smaller actually. It's the same red it was when it happened. It just is a blister now and it goes from itching like mad to slight pain. I'm just wondering how long this process goes on before it heals I