Why is my iphone sayi g try again in 8 hours?

You can’t get past it without resetting your phone to factory settings. You need to identify why your passcode changed; passcodes don’t change by themselves, someone had to change it.

If your device has iOS 15.2 or later installed, you can reset it without a computer; check out this link→How to reset your iPhone, iPad, or iPod touch when you forgot your passcode - Apple Support. Otherwise you will need a computer:

See this Apple support link→If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

Or watch this companion video ⬇️

After restoring the phone using one of the methods above you can restore your most recent backup.

If you did not change your passcode, someone else did.

At some point, you will exhaust the number of tries and the phone will display an Unavailable screen. Then, you have to reset the phone and set it up again.

You won't need a computer if you follow the instructions just below:

If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support