Thanks for the query. It appears that the condition you have is acanthosis nigricans. There are many ways to approach the disease. The disease is basically a manifestation of insulin resistance. Post retinoid pigmentation can sometimes occur and need specific management. In the clinical photograph provided, it is not evident, so exact recommendations cannot be made. Usage of a sunblock will help.
Meet a qualified Dermatologist for exactly understanding the severity of disease. You may need certain blood tests to understand your problem.