EE was helping assemble an excavator. Attempting to attach arm to boom with a steel pin (273.25 lbs.). Pin was held in place with a nylon strap. Pieces were misaligned. The EEs began to remove the pin and pieces shifted, causing the injured EE's finger to be pinched between the pieces, causing soft tissue injury. EE was treated for degloving of the distal phalanx of fifth finger.