How to unlock phone without computer I forgot my passcode

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

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.