Student or Learner
“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’m not hungry
I mentally cringed so hard, I’m surprised I didn’t sprain something.??
The main meaning of 'cringe' is something physical - withdrawing from something unpleasant (use a dictionary for more information) - an example would be shrinking away from an expected attack.
'Cringe' is often used figuratively, to suggest that sort of reaction, but only on a mental level: in an embarrassing situation, say - 'Oh no! I didn't just say that did I?' Something that is embarrassing can (informally) be referred to as 'cringe-worthy' or 'cringe-making' - going to work in your bedroom slippers, for example.
In your quote the mental cringe is extrememly violent. The idea of straining something is also physical. An athlete might 'strain a muscle' in a sprint. So the quote is hyperbolic - it is (almost - far be it from me to under-estimate the power of the mind) impossible to suffer a sprain as a result of a mental effort.