Lump on right clavicle, pain, x-ray report normal, taking vitamin d

My father has been having pain in his left neck to shoulder for a few months. He does a lot of physical labor at work with horses for the past 30 years, therefore always has some pain. He noticed the other day that he has a hard painful lump on his right clavicle . His pain is mostly in his shoulder when he s up and about and hardly any pain at rest. He had an X-ray which was normal. He also for the last two months has been taking more than the recommended dose of vitamin d-3 daily, which he stopped taking the day he found the lump. Do you have any thoughts on what this may be?