What sharp pain when mobile and immobile in the left shoulder mean and what should i do?

RICE: What activities led up to the problem? Rest the shoulder, consider applying an ice pack to the shoulder several times a day. The ice should itself not touch the skin. Consider a water in a baggie with the ice in it. Wearing a sling will help to rest the shoulder. If all of this fails to help, I would call your doctor for additional ideas or referals.