How to unlock phone without computer I forgot my passcode

If your iPhone says it is disabled, you must use a computer to erase it. This article explains what you have to do --> If you forgot your iPhone passcode - Apple Support

If you have updated your iPhone to at least iOS 15.2 and the message says your iPhone is Unavailable, you can erase your phone without a computer, by following the directions in this link --> If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support

Again, that is ONLY if you see the message your iPhone is Unavailable. If you see your iPhone is disabled, a computer is required. If you don't have one, visit a friend who has one, or visit your Apple Store Genius Bar and they can help you there.

If you have iOS 15.2 or higher installed on your iPhone 8.....you might be able to erase/reset the phone without using a computer.

This Apple Support document has the details:

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