The procedure you describe is one used to treat adults who have trouble retracting their foreskin during intercourse. It also is only to be done after a round of steroids and stretching exercises have failed (this treatment is also only for adults.)
When the opening of the foreskin is too narrow to allow a rapid flow of urine through in young boys all that happens is that the foreskin balloons. This is pretty common and completely harmless.
The following are all possible causes of pain during urination:
Separation, which goes away on it's own in 24-48 hrs, but may recur several times.
A small scratch on the foreskin, which will heal on it's own.
Yeast infection, which a PP pointed out is likely and easily treated.
A bacterial skin infection, which would be treated with bacatricin cream (not neosporine though.)
UTI, which is treated with oral antibiotics.
STD, I assume this one isn't a possibility considering age.
A kidney stone, or small crystals in the urine.
Dehydration, which is treated by drinking more water.
Considering that diabetes causes one to drink a lot and then pee a lot, his penis may just be plain old irritated from it all.