I've shot myself with nail guns twice.
Once with a rented roofing gun that kept jamming. I got used to just reaching over the top carriage and re-adjusting it, and had my finger on the trigger (set up for "bump shoot"). Grabbed the vise grips from my pouch, yanked it out (yeah, the wire collated barbs are fun) Grabbed a McD's napkin from my pouch and some electrical tape and wrapped it all up while I was on the roof. and went back to working.
Second time was a 16ga finish gun, nailing a stair handrail return. Nail just caught the grain wrong and came straight out into my hand holding the pieces.
The impact was the worse pain, not really the penetration.
I nailed my foot to a subfloor years ago and had to use a catspaw to pull the nail out. Ringshank of all things. Holyshit it hurt coming out. That one looks like its just under the skin. A few drinks and a good pull he will be fine. Of course cleaning it out after they pull it will be an awesome test of his pain tolerances too......:boobeyes: