all of the crows probably have pretty high pain tolerances. kaz developed it through street fights where he ignored and pushed past the pain to prove a point, and then even more so after his injury. inej likely also dealt with several injuries as a child training in acrobatics, and I imagine jespers experience was similar, although he simply got up to all kinds of trouble rather than having a specific cause.
nina and Matthias were both training to be soldiers as a young age, which likely meant hard training, and wylan suffered abuse his whole life. all of these children, these teenagers, I imagine went through staggering amounts of pain and would genuinely horrify full grown adults in fights (or torture situations, as with wylan) with how much they could go through and stay on their feet