nRF52840 (SENSE) module permanent storage

I am designing a BLE Beacon system using nRF52840 module and the Adafruit BLE library.
I want to use the Arduino IDE. I need just to store, let say 20 bytes, less than 100 times in the life of the product.
Is there a way to store some value in the aditional FLASH of the board, or the main FLASH ? and if yes, could you give me some examples of Arduino code ?