Like the urethral opening? If its that, I have no idea. Or just the tip of his penis? Could just be some irritation from the diaper. Have you tried a dab of diaper cream? Also that area has lots of blood vessels so sometimes it may seem more red than others.
The hole on my son's penis was red and last time we were at the doctor I asked about it and he said it looked normal. I would ask your pediatrician though.
Re: baby boy red urethra