When I say 'pain', what do you think of? Physical pain? Emotional pain? Mental pain? How do you distinguish between these? Can you? Or is pain just pain? Pain does not just have behavioural consequences, there is something 'it is like' to be in pain. If the feeling is absent, you cannot claim to be in pain. It is not possible to imagine a pain, it is a thing of a moment. You can remember that you were 'in' pain, but you can't summon back the what 'it is like' of that pain from memory, you are either in pain in a particular moment or not.
Physical pain seems straightforward: bring affliction to a part of the body, and pain will be felt by that person in that part of their body. Awkward that it has been reported by some amputees that they can still feel pain and other sensations in the limb that the doctor knows has now been removed. And can you expect two people with exactly the same injury, to feel exactly the same pain? How do we know? Can you describe your pain to someone, as is sometimes asked? When people say they can 'feel your pain', can they?
What of emotional pain? That searing pain in the chest or gut apparently caused by tremendous upset, hurt or grief. Mental pain? The head or brain aches associated with concentrating hard on difficult intellectual problems. In that we apparently still feel both emotional and mental pains in specific areas of the body, perhaps all pain is actually physical? Or all in fact mental? What is clear, is that you ought to be very careful before ever making a judgement about anybody else's pain, of whatever kind. Being in pain is to be feeling in pain, and you cannot feel theirs, only your own. It might be the same, but you don't know.