This is Dr. David
rashes of the top of the penis can be a sign of infection of the glands penis.
you should see a doctor to see if you need antibioitc therapy or antifungal treatment for your penis head to treat the rash.
once the rash is treated, it can be easier to pull back the foreskin
you should be pulling back the foreskin daily when you shower to clean with soap and water.
would you like to post a clear jpg photo of the rash of the head of the penis so I can better help you?
here are instructions to how to upload a clear jpg photo from a computer.
type a word in the textbox and highlight it
then select the "chain" icon above the textbox or the paper clip icon to upload a jpg
this opens a window where you can click next to the text box to select the jpg or pdf file on your computer to upload into JustAnswer