Hello prashantfromgwalior! Thank you for participating in the Apple Support Communities.
We understand that when taking a photo with your iPhone 12 Pro, you're seeing a green lens flare. We'd like to look into this with you to see how we can help.
This can happen when incoming light is at an angle that reflects off the surfaces inside the camera. Moving the camera slightly to change the position of the light can help, or shield your lens with your hand.
The following article also contains camera related tips: If the camera or flash on your iPhone, iPad, or iPod touch isn't working
Make it a great day!