[an error occurred while processing this directive] and Can't Fix It

I’ll try to be direct about my issue. While updating a site I was working on, I uploaded a picture (that I created, by the way) that somehow corrupted the entire site. Now, the only thing that shows up is this notice against a plain white background: [an error occurred while processing this directive].

I eventually tried to delete the image via FTP but I can’t find the photo anymore (yes, I know where to look, the image just isn’t there) and now I have no idea why I can’t get back into my website. I listed what I did sequentially, so no, I didn’t install or update a new plugin in between, I didn’t update WordPress version and I didn’t touch any permalink settings or otherwise. The way it happened, quite literally, is I uploaded an image as a feature image on a post, it told me there was a problem uploading the image and then when I tried to click on the Dashboard link, the [an error occurred while processing this directive] notice appeared. I can’t access any portion of the site’s WordPress install and aside from that image I tried to upload, there’s nothing else new to the site that would have prompted this.

I’ve read other threads about the notice and the fact that ultimately, they either just waited or adjusted permalink settings to fix it. I’ve waited three hours now and there’s been no change. I’ve deleted all of the uploads I uploaded today and still nothing. Any help would be greatly appreciated!

P.S. I get that solidarity makes people feel good, but honestly, if you don’t have an answer, I’m not so sure what saying “Yeah, I don’t know what to tell you” contributes to finding a solution. Thanks!