When you took your shiny new Note 7 out of the box, did notice the weird accessory tucked away at the bottom of the box? Don't throw it out! You're going to need it if you ever need to change the tip on the S Pen should it ever get bent or lose get worn out.
The tool is essentially a pair of tweezers designed specifically to grab the S Pen's removable tip and pull it out. Trying to accomplish such a feat with just your fingers is near impossible, or so it seems after trying for several minutes myself.
Also included with the Note are several replacement tips, in both black and white. After removing the now defunct tip, you can set the tool aside and push the replacement tip into the pen using your hand. For good measure, it's not a bad idea to lightly press the pen against something like a notebook or your hand to make sure it's not going to fall out. Of course, don't go overboard; just use enough pressure to make sure it'll stay in place.