Worst knife related injury was when I was 13 or 14 and I was chopping weeds for a local farmer in one of his fields. I was using a relatively dull curved-blade machete we had laying around, I had thought about sharpening it, but never got around to it, good thing too. I was aiming to chop through what looked like a small tree, maybe an inch and a half in diameter or so, and presumed it would take several whacks. Went clean through on the first try and since I wasn't expecting it to, I wasn't as careful as I should have been with where the rest of my body was.
The machete ended up sticking in my left arm about 4" above my wrist, didn't quite make it to the bone, thank goodness it wasn't very sharp. I immediately dropped the machete and grabbed the wound with my right hand, clamping down with considerable force. I hopped on my bike and rode a mile or two to the farmer's house where his wife helped bandage up the cut. I probably should have had stitches because the 3/8" x 2" scar I've on my arm for the last 25 years would be a lot smaller now.