Nail pops and blisters on interior walls and ceilings are not an uncommon occurrence in gypsum wallboard construction (drywall) and are usually associated with normal wood and material shrinkage.
To minimize the likelihood of nail pops, avoid excessive temperature and humidity changes in your home. If you are leaving your home for an extended period of time, adjust the thermostat to a setting no lower than 55 to 60 degrees Fahrenheit in the winter and no more than 80 to 85 degrees Fahrenheit in the summer.