Little crack on my Ipad 10th

Cracks can only be resolved by replacing the entire screen assembly. Cracks are notoriously difficult to prove as being due to a manufacturing defect - and are therefore very rarely covered by warranty.

Apple does not supply replacement components for self-repair of an iPad.

If you have benefit of an active AppleCare+ plan, your iPad and screen will be covered for breakage or other accidental damage.

You can check availability/eligibility for repair - and associated cost for your country/region - here:

iPad Repair & Service - Apple Support

In addition to Apple's mail-in repair service, you can arrange repair at the Genius Bar of your local Apple Store or Apple Authorised Service Provider (AASP):

Genius Bar Reservation and Apple Support Options - Apple

Cracks/scratches would fall under accidental damage and would not be covered under warranty. You would need to have it repaired by Apple or an authorized repair facility in order to keep the remaining warranty valid. 3rd party repairs would not be a good idea.

Using a Screen Protector after damage occurs is unlikely to prevent the existing damage from spreading - or prevent inevitable touch screen issues that will become increasingly apparent as the crack worsens.

The relative economics of replacing the screen can only be determined by you.

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 while expensive will be somewhat less than the cost of a replacement iPad.

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