Hi

Unfortunately if you have a forgotten/unknown device passcode, or have a disabled device (device unavailable or lockout screen), you have no option but to erase the device. However, you can eventually restore the data and settings from a backup you made before the device was disabled, or if you were using iCloud to store that data. If you end up having to use a computer and you do not have one, borrow one from a friend, or go to an Apple Retail Store or Apple Authorized Service Provider. You can also use a PC with iTunes. You will likely also need your Apple ID and password. All Apple mobile devices follow the same general procedure but the link below and other links off it provide system and model specific instructions:

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

If your phone is disabled there is no way to unlock it without resetting it to factory settings. That’s why it’s important to back up your phone frequently, ideally using the built-in automatic nightly backup feature.

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.