Suggest Treatment For Rash On Leg And Headache

I have a rash on the back of my leg (its about 15cm across and down most of the back of my thigh). I ve also been having headaches today and I ve been having head aches for a couple of weeks, worse than I ve ever had before, more like a migraine, aversion to light, sound motion, etc. I saw a nurse a couple of weeks ago and she said take painkillers for the headaches and possibly stress, (I thought it also might have been humidity at the time when it was foggy). To ease the headache today, I had a bath and since then the rash on the back of my leg has got bigger, more inflamed, hot, itchy and painful. Rang the GP and they can t see me until Wednesday. Do you think it s worth a trip to the walk in at a hospital? (headaches still persistent, but less aversion to light tonight, general lethargy even though I ve been sofa dwelling all day).