Walter Emanuel Jones lost his left middle finger in a childhood accident when he was four years old. While playing with his sister, they found a Derringer pistol that they mistook for a toy. When the gun wouldn't fire, Walter tried to "fix" it, and as his mother entered the room, he accidentally pulled the trigger, causing the gun to discharge and shatter the bone in his finger. Doctors were unable to save the finger, but thankfully, the safety being on prevented a much worse outcome.
One of the advantages of being a Power Ranger is that your molecules age slower due to a phase/time difference in the multiverse and also the use of their powers over time....