You need to use drywall screws to tighten down the drywall next to the popped nails. Pull the nail if possible, or drive it flush, then repair with general purpose compound, sand and repaint. This can occur where drywall is fastened to trusses with a live bottom chord or second story joists with excessive deflection, or by the use of the wrong type of nail. Using drywall screws in the affected area will usually prevent further movement.