Considering the symptoms, one common possibility is of- yeast infection. It can be treated with anti fungal medications.
The other common cause is- penile papules .They arise from sebaceous or sweat glands.
As such, is should not be ignored. My opinion is that, he need to be seen by Physician ,for the evaluation and the management.
Well, the rash and the itching can be possibly due to yeast infection.
Clinical diagnosis is important in this case. My opinion is that he need to be seen by Physician for evaluation and management.