What Causes Rough And Peeling Skin At The Back Of Nose?

Hi, The skin on the back of my nose is peeling. it looks like a spot half penny size. Not lifted, no pain, but constantly peeling. For years now. It started in 2000 after vacations in Panama as a dark spot. Later it was treated by family doctor with liquid Nitrogen. Since then the spot never healed with normal skin. It is rough and peeling. The Dermatologist told me not to worry . Thanks in advance. Ilana.