Nail pops are one of the easiest repairs to do. The first thing that needs to be done is to reset the nail (i.e. the head of the nail should be slightly recessed). This can be done with the rounded end of a screw driver or a ball peen hammer, tap lightly until nail head is recessed into a small dimple, but do not break the paper or through the board. Next step is to take a small putty knife (a 2" or 3" blade works well) and a small amount of your favorite drywall compound. Using the swiping motion of an "X" (meaning, swipe from left to right, then from top to bottom) fill dimple level with compound. It is possible that you may have to fill the hole twice. The first time may shrink, requiring more compound to be added. Sand smooth, prime and repaint the wall.