Hello, thanks for using HCM.
From your description you must be in severe pains and you are probably suffering from an injury to the rotator cuff
muscles which are a set of muscles that help in rotation of the shoulder and also in raising the arm above the shoulder. the lesion could vary from a simple contusion
of muscles to severe lesions such as a torn ligament. Pain that is associated with a ligament or bone injury
appears immediately following the trauma and usually is accompanied with swelling and loss or reduced function at the particular joint.
You should consider seeing a doctor at least for an initial examination and for an x-ray that would rule out fractures or dislocations and will prompt immediate special treatment if need be rather than waiting for a couple of days in which case you might aggravate the lesion.
For the main time, you should maintain the sling and get some pain killers like paracetamol
tablets to control the pain as you go to see your doctor.
Best regards and hope this helps.