Suggest Treatment For Spreading Dermatitis From Hand To Genitals

Hello, I'm a 21 year old male (5'8", 190lbs) who has never had sexual intercourse. I have dermatitis that I treat on my hands but for the past 6 months to a year it seems to have spread to my genitals so I itch a lot down there. As a result, I scratch and have some open wounds from time to time. I say all of that just in case it might be helpful. My issue is that I have a bump about midway up my penile shaft that is sort of below the skin and sort of feels like a knot. It is very easy to detect when erect (visible and feels sort of hard), but when not erect, it is not visible and not as hard, and is therefore hard to locate. I noticed it close to a week ago. What should I do?