iPad pro gen 5 screen is faulty

Your fifth generation iPad Pro uses a miniLED backlight that has ~10,000 individual LEDs, these being grouped into ~2500 local dimming zones.

As illustrated by your photo, at least one dimming zone has likely failed. The only remedy is replacement of the faulty screen assembly.

For practical purposes, in lieu of repairing and returning your own iPad, Apple usually exchange the iPad for a renewed/refurbished iPad of the same model and specification. The cost of the exchange is the same as would otherwise be charged for repair. Unless you have benefit of an active AppleCare plan, an out-of-warranty repair will be expensive.

As for out-of-warranty repair costs, Apple offers a fixed-price price repair. You can verify eligibility and cost for your region/country here:

iPad Repair & Service - Apple Support

If you have an active AppleCare+ plan, the cost of repair is reduced to a small excess/deductible fee.

Could be damage to the screen from pressure or an impact that may have seemed minor. Getting it inspected by Apple or an authorized repair facility would get you a more accurate diagnosis and let you know what your options are.

if it's under warranty then try

Legal - Hardware Warranties - Apple