I had one about 7 or 8 years ago related to some repetitive motions I had to do as part of a field work project. It is basically inflammation in the shoulder joint causing the bursa sacs to pinch a nerve when you move the shoulder in certain ways. I tried taking Aleve for a few days, but it really just took the edge off, but never really got rid of the pain or the inflammation causing it. So the doc gave a cortisone shot and it was gone within about 24 hours.

What I am dealing with now is similar in nature, but in my other shoulder. They are calling it a nerve entrapment. It is caused by spasms in the muscles around my shoulder blade pinching the nerves running from my neck across my shoulder and down my arm. because there isn't a localized cause with what I have now, all they can do is work to loosen up the shoulder muscles to relieve the pressure on the nerve.

If they give you the option, take the cortisone shot. It is a few moments of pain but will almost immediately reduce the inflammation causing the majority of the pain.