Nail sticking out other side of wooden door - how do I remove the sharp end?
You can spend 30 min ( or much more ) filing them down and who know how much time repairing the file mark on door or you could spend 10 min removing them and replacing them with an appropriate size SCREW. 

Tap the point of the nail until the head of the nail is out far enough to get a pry bar or the claws of a hammer on it and pull it out (gently and protect the door from the hammer or bar with a scrap of wood).

Install a screw that has a larger diameter that the nail and is shorter. If the door is hollow you may need an anchor for the screw and if it is hollow a nail is not the appropriate fastener.