When I fast I do not get kidney pain (or any pain). This may be due to a lack of hydration. I would hydrate and if it doesn’t go away quickly, break your fast and see a doctor. This may not be due to fasting at all.
Pain is not something you should experience due to fasting. It is not normal and should be explored like you would any other pain.
Make sure you are supplementing with enough electrolytes. There were posts in a sub a couple of months ago from 2 women who got kidney damage from fasting too long without electrolytes, which help your body keep hydration where you need it. Kidneys use salt in the process.