Pain in your left arm might be a symptom of a bone or tissue injury. Possible injuries include: bone fracture in the left arm or shoulder bursitis, when a bursa or sac of fluid between bone and soft tissue becomes inflamed carpal tunnel syndrome, or compression of one of the major nerves to the hand as it travels through the wrist herniated disk, or a tear in one of the cushioning disks between the bones of your spine rotator cuff tear tendonitis, or tendon inflammation