My DS has never had a UTI but somehow the skin at the tip (not circumcised either) did split. Mentioned it to a friend and she said it had happened to her son a month or two earlier and that it was a common occurrence around that age. I'd never heard of it before but can't say I have a whole heap of friends with boys. I took my son to the GP and he wasn't really concerned at all and said it'd heal itself and to keep an eye on it that it didn't get infected.

Whatever it happening, hope it gets sorted soon. Can't be pleasant for your poor DS