On the face, it is a silly question. After all, everyone knows what pain is. But there are many issues involved that complicate what seems to be a relatively simple issue.
In the first place, all pain is subjective. In other words, I can only know the intensity of my pain, and I can never know the level of yours. Medicine has tried to objectify things by creating various pain measurement ratios, but again, they are still entirely dependent on the individual's responses.
All of us have different pain thresholds. Some of us seem to bear pain better than others, and we all react differently to pain. An emergency ward recently admitted a workman whose foot had been pierced by a nail. He was in agony. But when the nurses removed the boot, they discovered the nail had missed the foot completely. When the workman saw this, his pain vanished.