How to unlock or restore Safari

Try Force Quitting Safari (either Activity Monitor or  (Apple) > Force Quit) and then hold Shift and click on the dock icon to open Safari. This should fix your issue.

Reinstalling the system drops a new functional system and then migrates all user data and settings in place, so you don't lose anything.

If no one has a more surgical fix, I would boot to recovery (Internet Recovery is a nice option if you have somewhat new to new hardware) and you don't have a USB installer handy. You can of course download the installer and make a local installer from the App Store, but recovery is the recommended way to fix this and other issues where a system framework or critical app like Safari gets broken.

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Before you reinstall:

• Have you verified that making a new user account (System Preferences) and logging in there is still broken?
• Have you also verified this doesn't resolve itself after a restart?

If it's not the system, you will have wasted time reinstalling and have to fix your preferences / settings if that's causing safari to break. It's less likely, but I've seen user corruption cause this on occasion.

There's no harm in trying recovery first, just these might save you time if you are not keen to reinstall for any reasons.