Site backend error, no changes made

I installed this plugin on a client website, looking to edit the capabilities for the author role. Before i made any changes, I opened an incognito window, logged in to the account with the role I was going to edit to check out what capabilities it presently had before I made any changes and the backend is broken. Just a blank screen. The frontend seems to work fine, I see the toolbar at the top, but when I try going to the backend, I get a “WordPress > error” in the title and a blank screen.

I’m currently logged in with my admin acc. and I fear that if i sign out i’ll suffer the same fate.

Is there anyway to fix this?