Hello,
It can be due to normal discoloration of glans (glands) or hyperpigmented skin. If the rash persists as papules then lichen planus should be ruled out. Lichen planus is an inflammatory
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.