Bone spurs are generally not something that would inhibit activity depending, of course, on the symptoms and exact location. If pain is present, it's most likely caused by the spur pressing against other bones or soft tissue. In most cases, bone spurs can be cared for by way of simple therapeutic measures such as ultrasound, and the like, with surgery as a last-ditch resort. Assuming the X-ray showed minimal ossification, I would have him seek the necessary treatment and monitor his pain while throwing. With some ibuprofen along the way, he should be fine.