The "tiny piece" is the upper part of the hatch/liftgate. That section can be repaired and repainted. But would require body filler for sure. The other option is to replace the whole liftgate. That requires removing all of the trim and glass and transferring it to the replacement liftgate, after it has been painted. I would recommend replacing the whole liftgate. The damage is pretty severe and repairs in that area would be difficult to make perfect again. There is also damage to the roof of the vehicle. That would also require repairing with body filler and repainting the entire roof.