I accidentally hit the fingerprint unlock button and it cracked now it’s very hot

The physical Home Button incorporates the TouchID sensor. If damaged, this requires repair - as, sooner or later, you will encounter a condition that can only be resolved with a fully functional Home Button.

As for the TouchID sensor, this is an active optical/electronic component. If it is becoming hot, this indicates a malfunction that may cause damage to your iPad. Similarly, the optical glass may present an injury hazard.

You might be well advised to discontinue use pending repair.

iPad Repair - Official Apple Support

Genius Bar Reservation and Apple Support Options - Apple

Whether the active TouchID sensor is built-in to the Home Button - or the Sleep/Wake (Power) button of the recent models of iPad Air - the outcome is the same. Broken physical buttons will, sooner or later, inhibit recovery actions.

As for your Sleep/Wake button becoming hot, the TouchID sensor is a delicate electronic component - that if damaged may malfunction or overheat. Excessive heating might suggest that a short circuit or other electrical overload condition has occured due to damage. If not repaired - and/or the iPad used whilst the fault persists - your iPad may suffer more extensive damage to its electronics.

You would be well advised to fully shut-down the iPad until such time as it can be inspected and repaired by a qualified technician.

It really doesn't matter which button

As Lotus Pilot has already stated, you need to get that iPad repaired, now.

You NEED that button and sooner, than later, you are going to need that button and it will no longer function OR function properly.

If that button is getting hot, then, DEFINITELY, that iPad needs a repair!

Do NOT screw around with this!

You need to search online for your nearest, “local” Apple store location and call contact phone numbers and call to make an appointment to have your Apple iPad diagnosed and options presented you.

Failing that,

You need to contact Apple support via the contact support link located at the upper right hand corner of every Webpage of these Apple support communities.

Use the Hardware Repair support category

OR

by installing and using the Apple Support app found in the iOS App Store.

Tap the iOS App Store link below.

https://apps.apple.com/us/app/apple-support/id1130498044

OR

Call contact Apple via the support numbers found in the link bekow.

Contact - How to Contact Us - Apple

Tap the link below.

https://www.apple.com/contact/

GET THAT IPad REPAIRED AND FIXED!

Best of Luck to You!