Are you talking about the pin seen here on the left (from this angle) side of the steering shaft U-joint?
If it is, that's the pin that holds the U-joint to the gearbox shaft collar at the end of the lower steering shaft and SHOULD NOT MOVE AT ALL! If it does, don't drive the Jeep (if at all possible) until you get a replacement lower steering shaft!
About two inches closer to the gearbox is the collar that mounts to the gearbox and it has a bolt that goes through the side. Looking down between the side of the fan shroud and the radiator:
If it is, that's the pin that holds the U-joint to the gearbox shaft collar at the end of the lower steering shaft and SHOULD NOT MOVE AT ALL! If it does, don't drive the Jeep (if at all possible) until you get a replacement lower steering shaft!
About two inches closer to the gearbox is the collar that mounts to the gearbox and it has a bolt that goes through the side. Looking down between the side of the fan shroud and the radiator: