I mentally cringed so hard, I’m surprised I didn’t sprain something.

[Tinkerbell]

“Hey,” I said, my voice way too loud, “if you’re, uh, hungry or something, I can see what’s in the kitchen. Running for your life and dragging a powerless demon all over the world probably works up an appetite,
huh?” As soon as the words were out of my mouth, I mentally cringed so hard, I’m surprised I didn’t sprain something.


I mentally cringed so hard, I’m surprised I didn’t sprain something.??

 

[White Hat]

That is a figurative way of saying the moment he uttered that statement some kind of a wave, quite powerful, went over him and made him shrink back for a second. He must have been scared or something.

 

[5jj]

He must have been scared or something.

It could also be embarrassment, if he thinks he's said something stupid: meaning 3 - Definition of cringe | Collins English Dictionary ,