Great-granny found it hilarious, which didn't really help. Asked DP for his male advice and he just said his mum would have clipped him round the ear.
Which I can't do!
So, any suggestions? He doesn't talk about it at nursery so must know it's not something you are supposed to talk about in polite company...
A friend suggested getting a book about bodily functions to read with him so that it becomes less of a taboo and more of an open subject and then hopefully he'll get bored. I will try this but wondered if anyone had any other suggestions?