Once the achar has cooled down, add vinegar and salt to taste.
Store the rishte ka achar / grated mango pickle in a glass airtight container in the fridge. As long as it's completely covered with oil, it can keep in the fridge for a couple of weeks. Make sure to use a clean and dry spoon to take out the achar.
Note: It’s important to take a heatproof glass dish to make this achar, and also make sure that the glass dish is small and deep so that the mustard oil covers the green mango / kairi completely. If the green mango / kairi isn’t covered by the oil, it can develop mold.