Suggest Remedy For Painful Hard Cyst On The Back

i have a cyst on my back and I am on antibiotics for it. I was told to come back to the nurse in 48 hours if it doesnt stop the pain. It got more painful So i went back and was told to leave it a day or two more for the antibiotics to take effect. But now it looks very angry and is sore constantly with a big firm area around the red bit. Should I go to an out of hours medical centre or wait until tomorrow? I m worried that it might be infected