I've had this on ocassion before, too - I don't think it's something you should worry too much about. I know what you're describing - the area is likely very tender to the touch. I've also developed this condition sometimes when masturbating freequently. It also could be related to jock itch
and/or the summer heat. Anyway - a good approach is to use a simple moisturizer on the affected area a couple of times a day. Also, try to give it a rest for a few days (not playing with it) so that it can get back in good shape. When the flaky skin and/or red tender area(s) are gone, he should be back ready for action - good luck!