Treat most pruning scars similar.
Cut back the dead stub flush or slightly concave to allow the new cambium to grow over the dead section. It will take ages for the new wood to grow over that protruding stub if left as is.
Any cut will heal quicker if the tree above the cut grows more so you may consider allowing this one to grow without any pruning until that cut is almost closed. Plenty of fertilizer will promote more growth and therefore heal the cut.
