The best so far I have come up with that people can relate to an experience they have had is to ask if they've ever had a really bad tooth, maybe one that needed a root canal, and they couldn't get in right away because it was a weekend or holiday.
They usually remember!!
I tell them THAT is nerve pain, the throbbing, aching, shooting, stabbing attention-capturing, sleep-destroying PAIN. That they had one, relatively short nerve that was really PO'd at them for a few days and kept them from normal activities such as eating, drinking, resting, enjoying themselves.
Then I tell them I have several, some of which extend all the way from my neck to the end of my fingers, and they've been PO'd for 3 1/2 yrs.
It's funny how the mention of severe tooth pain can make believers, but it does!