Does a herpes rash go away in 2 days because i had a rash on my penis head with little bumps but with warm water went away? could it have been herpes

Not likely: Highly unlikely that herpes would go away in two days. There is no substitute for an exam by an experienced clinican.

Unlikely: The lesions associated with genital herpes usually last 2-4 weeks with initial infection and 10-14 days with recurrences. The small bumps you describe were likely related to irritation and prominence of the many sebaceous glands on the head of the penis (fordyce spots), or possibly a mild fungal/yeast infection, or possibly a reaction to a spermicidal, lubricant, condom, or other irritant.