Stuck or dead display pixels are unusual - but not unknown. There is an industry-wide scoring formula that is used to determine whether or not one or more pixels are considered to be a warranty defect.
If you purchased directly from Apple, you have 14-days within which to unconditionally return your device for exchange or refund. If within your 14-days eligibility, you would be best advised to make use of the opportunity while it is available to you - otherwise you will be reliant upon remedy under warranty. Depending upon your country/region, you may have additional statutory rights and remedies available to you.
In addition to the above, should you have opted to purchase the optional AppleCare+ cover prior to discovery of the problem, you may be able to make a claim.
Either way, you would be well advised to seek immediate contact with Apple Support.
You can contact the Support Team using the Get Support link at top-right of this page. Alternatively, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:
https://apps.apple.com/gb/app/apple-support/id1130498044
You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to assess your iPad:
Genius Bar Reservation and Apple Support Options - Apple
