I worked for a company once that installed a remote-activation killswitch in their drivers, as a secret weapon to force the customer to stay current on their maintenance contract.
The CEO was a fuckup however, and the code killed their system even without being activated - resulting in a bunch of angry phonecalls and some of the most egregious lying I've ever heard.
god, he was a piece of shit
Depends on the pain.
If it's joints or ligaments, stop immediately. Coddle the shit out of them.
Muscles, treat them like dirt, get shit done.