Zuko had seen that she wasn't holding it tight enough, even though he had told her to grip it TIGHT, and was about to tell her to wait, when she fired. He jumped out of the way to make sure the renegade arrow didn't hit him, and was on his way to Katara's side when she accused him of doing that on purpose.
"I told you to grip it tight," he said as he put his hands upon her wrists, gently tugging on in attempt to get her to remove her hands from her face - not even bothering to think about how she might react to him touching her.
In a surprisingly gentle and soft tone he said, "Let me see if it's broken. ...please?"