Sore In Hair For Years, Scaly, Itching At Times. Should I See A Dermatologist? Suggestions?

I have had a sore in my hair for years that doesn't heal. It covers with a white scab that is scaly. What is it? My doctor told me to leave my fingers off it and I try, but it itches at times. A little while, maybe a week, I get a black scab, but it imbeds itself into the lesion, and never drops off. Please tell me if I should see a dermatologist again. They put a shot in to the sore and it seem to get smaller and go away. Two years or so, it has come back.