DS2 (just 3) has been complaining, lately, of a sore willy. There is nothing obviously wrong there, it all looks fine.
He does seem quite anxious and upset when this happens.
I suspect it may just be him getting an erection, he fiddles with it because it's sore, which makes it worse, etc etc, but I'm a bit worried it might be something else?
(He's not pulling back his foreskin yet, I don't think.)