Ball players—volleyball, basketball, football, etc.—see injury from a finger bent backwards more often than others. When the ball forces the fingers to bend the wrong way (toward the wrist), it can cause a volar plate injury. The volar plate is a ligament that attaches the PIP joint (where the finger meets the hand) to the flexor tendons, which are attached to the bones. Acute pain right after the incident, swelling, and bruising at that particular joint are the most common symptoms.
Don't try to diagnose this injury on your own. Finger and hand pain that doesn't get better quickly on its own and/or with ice and rest usually requires medical attention. Treatments are different depending on whether there was just tissue damage (ligaments and tendons) versus a fracture (broken bone). An x-ray will aid your orthopedic doctor in properly diagnosing your injury.
Ligament or tendon damage only is considered a sprain or just soft tissue damage. Treatment often includes splinting or buddy taping to the finger next to it, special finger exercises (hand therapy may be prescribed), ice, and some time avoiding the activity that caused the injury.
Sometimes a small piece of bone will break off the main bone when the injury occurs. This is called an avulsion fracture, and it needs a specialized orthopedic hand surgeon to reattach it with wires or pins. Ignoring a broken finger or splinting it before it's correctly positioned can lead to lifelong pain and mobility problems.