Hi! First of all please stop cutting or rubbing your skin around your knuckles,it will only make it more darker and thick. The skin around this area could be dark, rough or thick because of several reasons. It could be caused by friction, dryness of skin, certain skin conditions, obesity, acanthosis nigricans or could be inherited.
Next Steps
Online or telephonic consultation would be better to guide you further
Health Tips
Apply a good hand cream twice a day. Use gentle or hydrating soaps or hand wash. Apply creams containing AHA or a low concentration of glycolic acid at night if you don't have any itching.