forgot my screen time password

Follow these steps

1. Go to Settings > Screen Time. 
2. Tap Change Screen Time Passcode, then tap Change Screen Time Passcode again.
3. Tap Forgot Passcode?
4. Enter the Apple ID and password* that you used to set up the Screen Time passcode.
5. Enter a new Screen Time passcode, then enter it again to confirm.

But, if your iPhone is disabled or in a security lockout, the only way you can get out of that is to erase the device.

If you're running iOS or iPadOS 15.2 or higher you can do that without a computer, see this for the instructions:

If you're using an eSIM, contact your carrier before trying these steps and ask for a QR code to set up your eSIM again.

1. From your device's Lock Screen, try to enter your passcode five times until the "[Device] Unavailable" screen appears and your device asks you to try again later.
2. When you're able to, continue to enter your passcode until the "Security Lockout" screen appears and you get the Erase [Device] option in the bottom corner of the screen.
3. Tap Erase [Device], then tap Erase [Device] again to confirm.
4. Enter your Apple ID password to sign out of your Apple ID on your device.
5. Tap Erase [Device] to permanently delete all of your data and settings.
6. When your device restarts, follow the onscreen instructions to set up your device again, restore your data and settings from a backup, and set a new passcode.

If you can't follow these steps, you can use a computer to reset your device.

If these steps aren't working or you're running a lower iOS or iPadOS version, please use a computer to get out of the security lockout

See this link for the instructions on how to do that

If you've forgotten your iPhone passcode – Apple Support (UK)