I would have thought it should have been immediately written up in an accident book. It was a needle! ANY place of work, dealing with 'clients' or not, should be writing up incidents such as these. Thankfully we've never had a kid get a needle stuck in his hand at work though ... (although there have been times when I've NOT wanted to say, 'Oi, stop running with those scissors!')
If nothing else, you could just ask what the protocol is for ... oh, let's see ... some hypothetical occasion where a nurse sticks a needle in your hand.