Make sure he is bathing/showering every day. It's likely that after a hard day or two of running around he has gotten sweaty and dirty causing the area to become raw. Give it a few days and if he isn't feeling back to normal then let him know he is going to the doctor. I'm sure the problem will fix itself. Hygiene is very important.
When I worked at the nursing home we were taught that that had to be pulled back and cleaned almost everyday or the skin could could reattach itself. The human body is amazing at how it likes to try to fix itself. Even my son who is circumcised (8) and didn't want to tell me about the sore on his let it go for almost a week before he showed it to me. I had to take him to the doctor turned out to be an ingrown hair follicle. So if it is a fair amount that won't pull back I'd say take him in if it's only a little amount then maybe Dad's idea would work, but then maybe the docs would have that numbing cream so it wouldn't hurt too?!? You could always call up and ask a nurse!
There is also an ask-a-nurse forum here on MedHelp :)
I have copied something for you , they may also use steroid cream if this doesn't work ask your Doctor about it The vast majority of tight foreskins can be suitably loosened within a month or so by persistent stretching twice daily.
When possible start by warming the penis. Use baby oil, Vaseline intensive care hand and body lotion, Nivea or any bland cream as a lubricant. Pull the foreskin forward away from the body several times then pull it back as far as it will go onto the glans (head of the penis} and hold it in this stretched position for several minutes. If done with an erection the stretching will be even more effective. Do this several times a day.
When stretching begins to make the glans (head of the penis} visible, grip the glans between thumb and fingers and roll the foreskin forward over the glans and thumb. Thus providing a larger platform on which to stretch. Hold it in this position as long as you can at a time - say 5 minutes. Repeat as often as you have the time and enthusiasm for. Later you will find there is room for two or more fingers to insert into the tight ring of the foreskin to stretch it further.
The glans is often uncomfortably tender to touch when exposed for the first time. This can be cured by deliberately handling it under water and frequently changing your grip. It will soon become less tender and reach a normal level of sensitivity.
It may become apparent that further retraction of the foreskin is held up by a short frenulum (banjo string - the tongue of skin in the mid-line underneath the glans) This is called a Frenulum Breve and can be cured by a small operation under a local anaesthetic called a frenuloplasty.
Take care to avoid trapping the foreskin behind the glans (Paraphimosis) when it becomes loose enough to happen but tight enough to be difficult to bring forward again. Seek medical advice early if you fail to return the foreskin to cover the glans.
Attempt to retract your foreskin every time you pee.
The foreskin and the glans develop as one structure. Natural separation of the two structures occurs gradually during childhood. The age at which the foreskin becomes retractable differs for each child. It may take until the age of 17 or beyond. This is normal. Forcing the foreskin to retract may cause pain, bleeding, scarring, infection, and adhesions. Therefore, the foreskin of a child should be retracted only by the child himself when he is ready to do so.
Boys are born with unretractable foreskins. This is normal and healthy.
Your son is normal for his age. When he pulled his foreskin back, he probably broke a fused area. I would not worry about the bleeding unless it continues. If he simply pulls his foreskin back as far as he can without hurting himself, then it will gradually get looser and retract more.