Have Pain And Itching In The Back. Had Acne Before. No Medication Till Now. What Can It Be?

Hi, I am 16 but have never really had back acne before, but last night my back started to itch really bad and was almost painfull, there were a bunch of little spots that looked like acne but right by my shoulder blade there was this really weird bump. I think it might have been a small brown not elevated birth mark i had before but it might also be brand new though either way it was never elevated before and i just noticed it last night cause of my itchy back, I don't think it was caused by my ithcy skin or me itching it but maybe it was, but I just noticed it how ever and its very noticeable. Its about the size of a pea much brown but its elevated and has a weird bumpy shape. It does not itch but the rest of that part of my back is really itchy And hurts in the middle of my back. im not sure weather or not to be worried about it but it just randomly appered i think, so please give me your opinon on what it might be or what to do. Thank you very much