Since the unconscious mind thinks in metaphors, associations, symbols, and images it is possible to influence it to do some extraordinary things simply by using a few analogies and telling a few stories.
For example, one client came to me for hypnosis to get ready for surgery. She going to have a fibroid growth removed from her uterus. Once she was in hypnosis, I used the analogy of an alarm clock to suggest the elimination of pain after her surgery.
Everyone knows how an alarm clock works. Its purpose is to alert us to wake up at a given time, and once it has done that we turn it off. If the alarm were going all day and night, it would lose its meaning, and just become background noise.
Pain is like an alarm clock. Its purpose is to alert the conscious mind to take care of some injury or illness. Once we have noticed and responded properly to the situation, it only makes sense to turn the alarm off. Otherwise, the alarm (pain) is just confusing, and meaningless.
My client reported that after her surgery that she felt sore, but fine otherwise. While she was in hypnosis, I had given her unconscious mind suggestions to only give her pain if she were doing something that might cause damage to the areas that had been repaired. The soreness kept her from doing anything sudden or strenuous.
Metaphors and stories are just one of the approaches used in hypnosis to create pain relief. Hypnotherapists also have a variety of other methods to help clients in acute or chronic pain.