I hit myself occasionally usually on the hand or arm with a stick. Since I'm old and on blood thinners it usually leaves quite a bruise. Never anything serious.
I did have an interesting experience once playing tympani. I play in a community orchestra and we had a guest conductor with us on Tchaikovsky's 5th Symphony. Big finale. Huge tympani roll at the end. We were to play in an off site hall using borrowed tympani and these drums had very squared off rims (read: sharp corners). The conductor said he wanted to work on the ending and he wanted us to play from the last letter to the end. When it came to the final big tympani roll, I nicked my knuckle on the rim causing it to bleed slightly. Not to worry, I thought, I'll go find a band aid for it. But the conductor said he would like to take that passage again. The force of the roll caused me to bleed more profusely. I figured I'll get a bandage for it. The conductor said "One more time from the last letter." The force again to play that last roll caused me to really bleed now, not only on the sticks but the rim of the drum. I finally got a bandage and thank goodness he didn't call "Once again."