Fracture of the Proximal Interphalangeal (PIP) Joint or Middle Phalanx: This is the most likely diagnosis given the history of trauma while trying to catch a ball, which could have resulted in a fracture. The inability to bend and limited movement due to pain are consistent with a fracture, especially if it involves the PIP joint or the middle phalanx of the pointing finger.

Ligament Sprain: A sprain, particularly of the collateral ligaments of the PIP joint, could result from the described injury, leading to pain and limited movement.
Tendinitis or Tenosynovitis: Inflammation of the tendons or their surrounding sheaths could be caused by the injury, especially if there was a sudden, forceful contraction of the finger muscles.
Dislocation of the PIP Joint: Although less common than fractures, a dislocation could occur from a similar mechanism of injury and would cause significant pain and limitation in movement.

Infection (Osteomyelitis or Septic Arthritis): Although less likely, an infection could develop after a traumatic injury, especially if the skin was broken. Missing this diagnosis could lead to serious complications, including destruction of the joint or bone.
Compartment Syndrome: This is a condition where increased pressure within a confined space in the body leads to inadequate blood supply to the tissues. It is a medical emergency that could occur after a traumatic injury and requires prompt treatment.

Ganglion Cyst: A ganglion cyst is a lump under the skin that can occur on the wrist or finger and might cause discomfort or limited movement, but it is less directly related to traumatic injury.
Tumor (Benign or Malignant): Although extremely rare, a tumor could cause swelling and limited movement of a finger. However, this would be an unusual presentation without other systemic symptoms or a more gradual onset.