Penis head is quite red compared the the surrounding skin. there is also a small sore inside. this results in a stinging sensation when urinating.
The best specialist to help you with this is a Urologist - you will need at least a doctor to diagnose what you may have going on and to prescribe oral medication to help with this.
If you are applying anything to your penis stop doing so, try to keep soap and things like shower gel away from the tip area of your penis