I forgot my iphone passcode

The only way to unlock your iPhone is follow the steps described in the Apple article:

(< iOS 15.2) -> If you forgot your iPhone passcode

If you forgot your iPhone passcode - Apple Support

• If you don't have a computer and you can't borrow one, you need to go to an Apple Retail Store or Apple Authorized Service Provider for help.

(iOS 15.2 and newer) you don’t need to have a computer -> If you see an iPhone or iPad unavailable message or Security Lockout screen

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

No can do. If you no longer remember your passcode, the only option is to erase the device. After the device is erased, you will be able to restore from the backup. As long as you were using the iCloud backup, this will put the device in the same state it was before it was erased.