Suggest Treatment For An Itchy And Flaky Brown Area Under The Armpit

hello,i have a small shady brown area under my armpit the size of a penny.It is quite itchy & a little flaky.Not sure if it has a lump had 4 about 1 month. I do suffer from psorisis in certain areas not here though. It is getting irritating & a little painful,also very stressed at moment,please advise.Rob.