SOS is on my screen

If your device has iOS 15.2 or later installed, you can reset it without a computer; check out this link→How to reset your iPhone, iPad, or iPod touch when you forgot your passcode - Apple Support. Otherwise you will need a computer:

See this Apple support link→If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

Or watch this companion video ⬇️

After restoring the phone using one of the methods above you can restore your most recent backup.

If you're referring to an icon in the status bar at the top that says SOS, it means that your phone does not have cell service and can only be used to make emergency (SOS) calls. Contact your carrier if that is the case.