Pigmentation is discoloration or darkening of some areas of your skin due to various causes. Most commonly, pigmentation occurs due to hormonal imbalance and over exposure to sun without any blocking agent. Pigmentation can happen in both men and women and of any age.
Treating Pigmentation permanently can only be done by its root cause i.e. what has caused it. If it is imbalance in your hormones, it would be treated from root once your hormones are balanced. Similarly, if it is due to exposure to sun light, you need to use sunscreen cream of any sun blocking agent while you step out in sunrays.
For a temporary solution, you can try out creams, serums and DIYs. One of the most common DIY face packs is= Gram Flour+ Honey+ Lemon + Rose Water. Apply this and keep for 15 minutes. Scrub and wash off with cold water.
You can also try apple cider vinegar, added with water and apply for 2 minutes. Rinse off.
Also, stay away from chemical-based face washes, creams and even shampoos. Do not apply deodrant on your face or directly on your skin to prevent pigmentation.
Make sure you visit a dermatologist if your problem persists for long. They may suggest you skin peels that can make a significant difference to make your skin even out.