You can use a simple, gentle facial exercise to stimulate circulation in your cheeks and make the skin look more radiant and more full. No extra fat or skin will actually develop, but your narrow cheeks may look chubbier if you practice this exercise daily.
Sit tall. Sit in a chair with your back straight. Pull down the shoulder blades and relax your shoulders overall, making sure that there is as little tension as possible in that area of your body. Your chest should be outward and open.
Open your mouth lightly. Imagine that you are carrying a normal conversation with someone at low to moderate volume. Open your mouth to the position you might usually have during such conversations. At this point, you must also curl both your lower and upper lip inward so that they cover your front row of teeth.
Simultaneously, you should pull the corners of your mouth back, bringing them as close to the molar teeth as possible. Both corners should be pulled back in the same direction and to the same level or vertical position of your face. Your chin should move forward slightly, as well.
Hold the face you have just made for a full 30 seconds. You should feel the muscles in your cheeks and mouth stretch. Release slowly to a normal resting face when done.