After dance class open shoulder. What's wrong with the bone inside the butterfly bone in the back that hurts

You said the butterfly bone refers to the lower back? If it is here may be and long time to keep sitting position related, mainly because of muscle fatigue or fasciitis caused by, so it is recommended to sit for a while to get up and move around, can be localized with a towel hot compresses, external use of Fuselin ointment or plaster, exercise lumbar and back muscles.