what you are describing sounds like a seborrheic keratosis which is a benign condition; however this needs to be evaluated by your dermatologist who will be able to either treat the symptoms and reassure you or do a biopsy to send the lesion to the lab for further evaluation and treat it as needed.
a new mole appeared on my back. it itches and burns is grayish and the size of a pencil eraser. is this skin cancer?