macOS app icon stuck on my screen
Turns out, I just had to reset the 'dock' process. I opened Terminal and typed

killall Dock


and pressed enter. The screen flashed for a second, and everything came back with my stuck icon gone.

If that fails, the issue may be with Finder (this is the case with the similar issue of Stacks categories "burned in" to your desktop background). Running

killall Finder


will address that.