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You should have your primary medical provider or a dermatologist look at this area. Any lesion that does not heal in a year's time needs to be evaluated to determine if it is skin cancer. The area behind the ear is particularly delicate and usually exposed to the sun in men. While you are at your doctor's office, s/he can draw labs to determine if you have a nutritional deficiency.
If you are talking about dry skin, then it is probably essential fatty acids that he was recommending (omega-3 and omega-6 fatty acid). Niacinamide is useful for treating inflammation and preventing onset of type 1 diabetes. Some people apply it to the skin. It is a B vitamin. Here are some links you might find useful. I urge you to have a doctor examine your ear in person. Making a diagnosis yourself based on an article is not prudent where your health is concerned.