The answer to this depends on the type of pain that is present.  If it is nociceptive (somatic) pain, the pain will last as long as there is tissue damage, inflammation and local chemical activation of pain endings.  Chronic pain of central origin characteristically lasts long after the source of the pain is resolved.  Pain of central origin can occur without any peripheral or spinal inflammatory process due to changes in the way nerves connect and due to changes in the way they carry nerve impulses.