I have just spent five hours in an admittedly very lovely German hospital being sliced up and put back together.
On Monday of last week I decided to have a bread roll at work. I was cutting into it with a serrated table knife and I didn't realise the knife was sharper than the ones I have at home, and cut my little finger. Oh well, thought I, that's annoying, and held it under the tap, but it wouldn't stop bleeding, so I ran to get help. Some of the office staff patched me up but strongly suggested I go to hospital. They even wanted to call an ambulance but I said I'd prefer to go myself.
Anyway. In A&E. Quite a lot of blood at this point. DH hoiked out of his very important first day in a new job 
, starting to feel that the labour breathing exercises aren't really cutting it. They took me off straight away into an operating room cum corridor (was v odd), gave me some pain relief in a little cup and started trying to assess the damage. There was some concern that I couldn't move the finger independently and then they realised it was also entirely numb on one side.
I had managed to sever the artery, nerve and tendon... so they stitched me up, gave me a tetanus shot and sent me home with a note to go to the next doctor.
After lots of back and forth between various surgeons and a system I'm still not sure I understand, they sent me off to a company who make medical adaptation devices to get a special brace (which costs €600, thank God for health insurance!) and an anaesthetist for a lovely chat about whether I'd like general anaesthetic or an injection in the shoulder to numb my whole arm (I went for the general, I don't like needles) and here I am 11 days after the accident with a "bionic arm"... They've repaired the tendon, and done microscopic stitches in the nerve, apparently, which is quite fascinating, but something in the op seems to have disabled half the nerves on my ring finger too. Currently only allowed paracetamol and ibuprofen, which is not particularly effective, but takes the edge off.
I've cut rolls like this for years. I've never thought anything of it. I know technically you're supposed to do it on a flat surface but I always (thought) I was paying attention and it would be fine. Clearly not! So here is my reminder to you and your teenage DC: it only takes a second to find a flat surface to cut on. Please make sure you do it and don't end up like me 
I was thinking I hadn't done much damage as I hadn't hit bone, but it really is quite serious.