This is actually really intriguing to me, especially as I barely even registered he was doing that, as someone who has not dissimilar tendencies myself. (For me it's a sort of weird response to prolonged physical+emotional discomfort. He probably wouldn't do meticulous self-harm like cutting, but is likely to tend to pounding on and slapping himself when really agitated. Possibly also violent hair-pulling...)

I don't think I can actually write a fic for this (though don't quote me on that, I've said such things before), but wow, I really really hope someone does!

(Gosh, I hope this doesn't count as prompt-jacking!)