Acromioclavicular (AC) Joint Sprain or Separation: This is the most likely diagnosis given the mechanism of injury (falling directly on the shoulder), the initial minimal pain that worsened with movement, and the limited range of motion. The AC joint is susceptible to injury from direct blows to the shoulder, and the symptoms described are consistent with a sprain or separation of this joint.

Rotator Cuff Strain or Tear: The patient's symptoms of pain and limited range of motion, especially with forced movement, could also suggest a rotator cuff injury. This is a common injury in sports that involve throwing or repetitive arm movements, like basketball.
Subacromial Bursitis: Inflammation of the bursa that cushions the rotator cuff tendons could cause pain and limited mobility, especially with movements that involve lifting the arm.
Adhesive Capsulitis (Frozen Shoulder): Although less likely given the acute onset, adhesive capsulitis could present with limited range of motion and pain, especially if the initial injury led to prolonged immobilization or guarding of the shoulder.

Fracture of the Clavicle or Scapula: While the patient reports no bruising and the rib tenderness has resolved, it's crucial to rule out fractures, especially given the mechanism of injury. A fracture could have significant implications for treatment and prognosis.
Brachial Plexus Injury: Although the patient denies tingling or numbness, a thorough neurological examination is necessary to rule out any brachial plexus injury, which could result from the fall and have serious consequences if missed.
Thoracic Outlet Syndrome: This condition, involving compression of the nerves and/or blood vessels that pass into the thoracic outlet, could present with shoulder pain and limited mobility, among other symptoms, and is important not to miss due to its potential for serious complications.

Osteonecrosis of the Humeral Head: This condition, involving the death of bone tissue due to a lack of blood supply, could be a rare complication of trauma to the shoulder. It's less likely but should be considered, especially if the patient's symptoms do not improve with conservative management.
Infection or Septic Arthritis: Although rare, especially without a clear source of infection, septic arthritis or an infection of the shoulder joint could present with pain and limited range of motion. This diagnosis is critical to rule out due to its potential for severe and rapid joint destruction.