Could Redness And Irritation Around The Penis Be Due To Unprotected Sex?

HI, i recently had un-protected sex and i woke up 2 or 3 days ago and noticed the left side of my penis head felt as if it had rubbed up against something repeatedly and was irritated, but upon close inspection i saw that there was no mark on my penis leading me to believe its a nerve issue. it doesn t bother me until my penis rubs against my underwear which is wierd because there is no visible sign of irritation, i am very worried because people online have said this persisted for years and it ruined their lives.