If the lesion is a red spot and its itchy as well over the head of penis, over the glans, then there is a possibility that it can either be a fungal infection or a STD. It is advised that you may visit your physician for a local examination and smear for culture to isolate the organism to ascertain the cause specifically and further offer treatment.
I hope I have answered your query in detail,
wishing you good health,
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.