Welcome to HealthcareMagic. It can be due to smegma deposits on the penis or fungal infection
. Don’t use any cosmetics on the penis; instead use some topical antimicrobials like Bacitracin
or Lotrimin. Wear cotton clothes, retract the foreskin daily and soak in warm water to clean penis and foreskin. In case the symptoms persist then please consult a urologist
Hope it helps you. Regards.