A cluster of painless blisters on penis shaft. the blisters look like water drops then pops after two days and crust over and still no pain or itching. i present no other symptoms no pain,itching, or burning. what all could this be?

Genital herpes?: This almost certainly is genital herpes -- usually painful but not necessarily. It could be an allergic reaction to something, or perhaps some other kind of dermatitis. If herpes, diagnosis is most accurate and treatment most effective the earlier you are seen; even a day or two can make a difference. So see a doctor ASAP. Good luck!