Hi I Went Into Ergent Care This Morning With Whet

Hi I went into ergent care this morning with whet I thought might be a staph infection.The doc thought so to he gave me a shot and wrote me a prescription for amox/cav and drew a line around the swellin and red area.now it is way past that area and i'm in a lot of pain. I was told if it was not better in 24 hours I should go to the ER,but it seems to be getting worse,should I wait or go in to the ER sooner? Thank you for your help