What Causes A Foreskin Rash And Penis Glans Marks After Unprotected Intercourse?

I had unprotected sex about 3 months ago at a party, noticed a red rash on my foreskin, this went down but now I have little red marks on my penis head! There no discharge or anything and it doesn't hurt to pee! My now girlfriend has complained that her private parts were swollen and a little painful but that went down after a day