So you're asking what to do about the fear of getting hit. Building up a tolerance to pain isn't exactly the same thing. Exposure is still the answer, you'll find that the fear is worse than the pain itself in most cases, especially with adrenaline running high. A lot of sparring will help but I'm sorry to say that there aren't many people who enjoy getting punched. Take a few good shots to the back of the head and it'll probably teach you to turn your back to your opponent... assuming you wake, the worst punches are the ones you don't see coming. Only other thing you can do is build up your speed and learn to get out of the way.
Push in head down and turn side ways and come up with the defensive left hooks with your right hand on your cheek and your chin tucked at all times. Are you wearing helmits? Maybe wear a sweater for that one spar too.
There is no training the chin. Chin is what you are born with. Tuck it in and keep it a mile away from punches. taking punches don't improve the chin a bit, in fact each punch will only deteriorate it bit by bit until it gives away. Don't believe those bullshit they show in those movies
Exposure therapy. Be careful, repeated bludgeoning to the head can cause brain damage with out warning. Try slapping instead.
In my kickboxing class, I am always worried about getting hit while sparring. I will turn my back to them and lean away. Anything I can do to get used to getting punched?
