Hi,
Most likely that you will have to replace the LCD screen assembly.
Here is a [https://www.youtube.com/watch?v=t0E-cwJ-eKI|video] that shows how to replace the screen in your phone.
Here is a link to just one [https://www.aliexpress.com/item/100-Original-LCD-Display-Screen-Touch-Screen-With-Frame-Replacement-for-Xiaomi-2-m2-mi2-2s/32214224348.html|supplier] of the replacement part. It is not a recommendation to use them. It is shown to give an idea of the cost of the part. There are others online that may suit you better. Just search for ''Xiaomi Mi2 LCD display with Touchscreen and frame replacement'' to get results