Fit and healthy 3yo boy, went to bed last night absolutely fine (although thinking about it he's complained of non-specific 'ow' the last few days). He's been up since 4.55am and can't or won't weight bear on his right leg. He wouldn't walk to the kitchen for chocolate, and he tried to get up to hug his sister good morning distracted and seemed to realise it hurt. No obvious injury or swelling and he's had infant nurofen. Any ideas? Thanks.