In your life, try to avoid sun exposure, pay attention to sun protection and eat a diet rich in vegetables and fruits containing vitamin C and vitamin E. Or take a tablet of vitamin C and vitamin E every day.
A doctor needs to be consulted to determine which disease is causing the cheek hyperpigmentation, as it can be caused by different diseases (e.g. melasma, nevus of Ota, brownish nevus of the cheek, coffee spots, post-inflammatory hyperpigmentation, etc.).
The treatment for different diseases is completely different and can be very counterproductive if treatment is not chosen properly.