Shoulder pain/issues?

My boyfriend jumped into a river over 5 weeks ago and didn't realize it wa as shallow as it was until his shoulder hit the bottom. He said it felt like it popped out and popped back in. He experienced a decent amount of shoulder pain that night and a few nights afterwards. When the pain did subside, there were still certain things that would cause pain to shoot through his arm like reaching behind him or putting his arm under his pillow to sleep. No issues lifting things really. He went to a chiropractor who insisted on checking out his neck? Which made no sense to me. To get to the point, his shoulder still hurts in some positions and even if he moves his fingers a certain way occasionally. Any idea what may be going on?