How old?? I think it's a natural phase at 2-3 where they discover they can say 'no' and want some control over their lives nursery or not. My all eating DS2 went through a phase of this when he was 2/3. He did go to nursery but I just put it down to the terrible twos and growing up. He's certainly over it now (just turned 4) as he seemed to wake up to the fact he was missing out!!!