Phew! What a crazy 30 mins!
Sorry about my hurried post, and thanks so much for the replies.
It's Jerry, and I have absolutely no idea how he managed it! Luckily he's downstairs with us, so I was able to spot it straight away. I had been out in the kitchen, and returned to the living room to find blood all through his cage and all over him. Obviously I panicked as I had no idea where it was coming from. I ran over to the cage, at the same time as shouting to the hubby who was in the garden. Jerry was sitting in the corner looking very sorry for himself holding his front, right foot in the air
I managed to stop the bleeding a few times, but it kept starting again. I think it's finally stopped now. I've cleaned him up the best I can, but I haven't cleaned up his nail as I'm worried the water will start it bleeding again. As far as I can tell, he hasn't ripped it off completely, but there looks like there is only 1mm or so left.
He's now back in his cage and concerned only with his evening bowl of veggies! I've changed his bedding and can't see any new spots of blood. He's walking on his foot okay, but is holding it up when he's sitting.
Should I try to clean the nail now, or leave it until the morning?