We are forced to speak of pain in terms of other, more visible objects, ie we are forced to speak metaphorically. The most common metaphor of pain is the weapon. We say, for example, that pain is shooting or stabbing or crushing.
When you think about it, these words are all being used metaphorically since most of the time we haven’t been shot or stabbed or crushed but are just imagining that something like this must be happening. So one way of talking about pain is to talk about guns, knives, and hammers, or the damage those weapons can inflict on the human body. There are also other ways to represent pain metaphorically which I discuss in my book. The bottom line is that we have to be exceptionally imaginative when it comes to pain or else it will remain incommunicable and invisible, not only for the sufferer but also for friends and doctors trying to help.