The worst I’ve ever hurt myself was learning the breakaway I didn’t put out my hand far enough and the yo-yo went right past my hand, up, and fell onto my head.
Otherwise some dangerous tricks are:
-Learning Horizontal, because it can slap you in the face
-Learning Finger Spins, because of the string snag onto your finger (this hurts quite a lot)
-Speed combos, because they can leave and slap you in the face
-Body tricks like around the neck tricks or leg wraps and stuff like that
-Rejections, If you mess up and don’t move the yo-yo to the side, it’ll hit you right on the hand.