Ouch. Hopefully you (and all of us) won't get this ulnar nerve thing or whatever it is
1000 ways of get injured playing chess

86. Replace the chess pieces with animals that don't like you and make the board bigger so the big animals could fit on them

Once I accidentally staplered my thumb, but not while playing chess. I was wondering what does a stapler do... Ouch!
Curiosity kills the cat.

Ouch. Hopefully you (and all of us) won't get this ulnar nerve thing or whatever it is
Sudden numbness in the ring and little finger, as well as in the corresponding part of the palm. While playing chess.
http://orthoinfo.aaos.org/topic.cfm?topic=a00069

92. Spouse hits you over the head when you won't break away from Online Chess long enough to take out the trash.

I can give you a real life example.
I got a guy banned from tournament play years ago for violent intimidating behaviour. He was waiting for me in the car park at the next tournament. Someone got hurt & there was a brown mark on my motorcycle helmet.
Your guess as to whose blood it was(smirk)

94. When your opponent says " I pinned you..." you thought you got hit by a pin so you get a heart attack at die
P.S. Actual sentence : I pinned your queen

#95: the board and the pieces are too clean, your opponent opens the window and the light of the sun gets reflected on one of the pieces, flashing in your eyes, leading in an epileptic attack

96. At a tournament, get punched in the mouth by opponent for noisely and sloppily eating greasy fried chicken at the chess board.

98. You lose brutally by 5 queens and you trash talk your opponent and he pulls out his gun and fires.
I damaged my ulnar nerve playing chess. The physician who conducted the nerve conduction study was convinced that I needed surgery. My orthopedic surgeon was willing to give it time before the slice, and with protection of the nerve (sleeping with a bath towel wrapped around my arm, for instance), the ulnar nerve healed in about two years. No surgery!
The injury was cause by propping my chin in my palm with my elbow on the table and leaning too hard as I was getting clobbered in internet blitz by some chap in Germany.