Hi, sorry to hear of your problem.
You say he bites-is it a bite or a nip? Collies do nip, yes, but it isn't acceptable. If he is healthy, then he's obviously not protecting himself. If he's skulking, then as indieanna86 says he realises his mistake. Please don't smack or shout-Collies especially don't respond well to that, but it's not great for dogs in general-my Collie is really nervous and if I was to hit him he'd just be terrified. I am no expert, and I see that advice given so far is conflicitng. Don't let him near kids without having him under complete control-mine can't go near kids at all, he hates them!! :S
My boy licks for attention, he's 2 so he's grown out of nipping us to notice him.
It is surprising that the person he nipped wasn't moving or acting unpredictably; if she was it would be understandable.
This has been more a ramble than directed advice; I just hope he (and you) are OK and take all the necessary precautions: you CAN be forced to put him down if he hurts someone.
Lisa :)