Lean on your elbow for five minutes.
It's the only way to make your arm 'numb' outside of Novacaine or some such local.
In the operation the woman isn't numb and is feeling everything.
Hypnosis does not turn off the nervous system, it adjusts and changes the mental reaction to the event.
As far as your nerves are concerned there is no difference to a gentle stroke or a hard slap. Different nerves appear to fire in different ways for each event but all they can do is fire a chemical reaction which sends a signal to the brain.
Now the ind becomes aware and decides from it's patterns of reaction what to do about it. IF the response should be hurt then you'll hurt. If not then you won't.
So with self suggestion - no such thing as self hypnosis - tell yourself it doesn't hurt and then prove it.
Of course you'll really have to believe - and I do mean really.