What Causes Rash On Back Inspite Of Being On Chantix For Sore Throat?

I have had a sore throat for a year. I went to a ear nose and throat Dr several times and he was very dismissive and diagnosed me with silent gerd. I started on zantac, quit smoking, drinking and lost weight but it only seems to be getting worse. Now it is tender to the touch on right side of neck. (where I can feel my pulse) my throat is visibly red but the Dr insists it s normal. I am taking chantix. Not sure if it matters but I also have a small rash on my back just behind my armpit. It has been there for 3 weeks. Does not hurt or itch or anything. Started as what looked like a 2 inch welt. It now resembles 6 little pimples but still there? Of course at this time I have no insurance. Any ideas? Please help.