How do you unlock an iPhone if you forgot the passcode?
forget iPhone passcode
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iPhone 7 Plus, iOS 15
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If you forgot a passcode that you changed within the last 72 hours, see the "If you recently changed passcodes, use your old passcode to temporarily sign in" section of: If you see a iPhone, iPad, or Apple Vision Pro unavailable message or Security Lockout screen - Apple Support
Otherwise, see the other sections of that article
If neither of the above is an option, you will need to use a computer. See: If you forgot your iPhone passcode, use your Mac or PC to reset it - Apple Support