When I had been yoyoing for a few months, I went to visit my friends in another city (I spent summers in Toronto, lived in Montreal). All excited to show off my new skills, I pulled my YYJ Speeder out of my pocket and threw a breakaway. Turns out the yoyo was knotted, got halfway down and snapped back, flew up, hit me in the nose. The impact was enough to both leave a long red scratch along my nose AND burst a blood vessel in my nose.
The result was tons of blood everywhere, and my friends not being very impressed with my skills
I rung my bell pretty good one time when I took a Mega SpinFaktor to the face. It hit me right in the eye, and it was almost swollen completely shut within a few hours.
A long time ago when I first learned guillotine, I had some problems with the yoyo being in control
I hit myself in the head with a metal yoyo after loosing control and landed on my foot (I was barefoot)