As you probably know, the rotator cuff are the group of muscles and tendons that surround the shoulder joint and are responsible for lifting and rotating the arm. They are commonly damaged, especially with heavy lifting or other forms of physical exertion.
If your doctor
examined your shoulder already and did not find any evidence of serious weakness or damage, then the most likely thing that is going on is that you are suffering from a bit of rotator cuff tendonitis, or inflammation in the tendons of the shoulder from heavy lifting. Fortunately, this means that you probably haven't torn the tendons or done any permanent injury
, as long as you take it easy and give your shoulder time to recover fully before going back to strenuous physical activity.
You should follow up on this injury closely with your primary care doctor
. They will be able to examine your shoulder again after a period of rest to determine whether or not it is in fact healing as desired. They can also give you advice on when it will be safe to return to physical activity, and whether or not it would be a good idea to take any particular pain or anti inflammatory medications.