I was using generative expand, but it looks like there's a part of the photo that wasn't expanded, but I'm unable to select it to delete it. I'm new to photoshop, so I'm just going through the tutorials now, but do you have any idea why my photo looks like a photo within a photo?
When you use Generative Expand as the Fill option with the Crop tool, Photoshop places the generated content on a separate layer that also has a layer mask where the original content was.
I can't see your Layers panel in the screenshot, but my guess would be that one layer may have been scaled while the other wasn't.
If that isn't the issue, would you mind posting a screenshot that includes your Layers panel? You would first need to either click Cancel or OK to exit the Select and Mask workspace shown in the posted screenshot.