What should I do here?


___________

Not a major issue.

1. you could allow Photos to continue its process. Migrating to a new operating system often requires the Photos app to reanalyze the pictures and that can take a very long time. Quiting Photos during that time can cause this message.

2. You could force quit Photos by using the force quit menu option under the Black Apple in the top left corner of your screen. That will force Photos to quit.

Restarting your computer will trigger Photos to continue its background processes. More info on what's happening behind the scenes in Photos here.