Having just been through a shoulder surgery where a large impingement was part of my problem, my understanding is that not all of them can be treated by rehab/non-surgical means. Apparently many athletes who participate in overhead or shoulder rotation type sports have these bone spurs. Many of us have them and don't even know it, because it does not cause pain. But when they get large enough that they put constant pressure on the rotator cuff, they may have to be removed. They were going in to fix my labrum anyway, so they took it out. In my case, the spur was causing me more pain than the cartilage tear. If it's bad enough, they may want to go in orthoscopically and clean it up.
Your doc might also suggest cortisone shots as a non-surgical option, and I'd be cautious about this. They seem to freely prescribe this, but my surgeon friends tell me to be really careful about getting more than one or a couple because it will eventually lead to break down of the joint and possibly arthritis later on. So do a lot of research and ask a lot of questions before going this route.
I'm not suggesting that surgery is your option but in my case, the spur would not have gone away without it. I had tried rehab/PT for nearly a year before deciding to have the whole thing fixed up. I'm not totally out of pain yet, but part of it is my own fault for rehabbing a little too hard (tendinitis). Otherwise, the surgery was successful. Looking forward to pain-free paddling soon.