What Causes Red Mark On The Penile Tip After Having Sex?

I recently had sex two days ago and developed a red mark on the tip of my penis, it chafes quite a bit, not painful. During intercourse things got a bit dry and I felt the tip of my penis stretch and felt some pain, so I used a bit of lube afterwards. After 30 minutes or so we finished and the next day noticed the tip irritated. Is this a sign of STD or chafing?