In standard medical terms pain is treated using medication however these are associated with myriad unpleasant side effects, some more serious than others. In NLP terms, pain is understood as a subjective experience that arises from the way sensory information (sights, sounds, feelings, etc.) associated with the painful stimulus is coded and processed in the neurology of the person experiencing it.

The key principles regarding pain in NLP are:
Pain is a mental representation or "map" created by the brain and not the actual physical reality itself.
This internal representation of pain is made up of sub modalities - qualities like visual size, brightness, location, sounds, feelings, etc. that make up the experience. By altering the sub modalities of how pain is represented
internally, the subjective experience of pain can be changed or even eliminated, without directly addressing the physical cause.