Hi there...I can understand your concern...you seem to be slightly under weight for your height. Ideal weight would be around 68 kgs for your height. Sunken cheeks usually are part of your bones structure. It's hereditary. Nothing much can be done about it. Try to build your muscle mass by eating foods rich in proteins like soyabeans, pulses, vegetables, egg white, boiled chicken. Also try excercises like swimming, cycling, gymming. Contact a dietician regarding diet chart.