Could this be an infection?
Hi - It looks like a sweat rash, my partner had something looking very much the same the Dr. told him it was caused by him wearing tight underpants. He went back to cotton loose boxers and it went away.
How long has it been like this?
Do not use soap or anything else to clean your penis with, use water only. Do not apply anything else to it such as skin cream, moisturisers or lotions, do not apply any lubes for sex or masturbation until the skin is back to normal.