Heat pump "clacking"

Greetings. About two hours ago, our heat pump (inspected in August) began clacking loudly–very much the sound a fan makes when a stick’s in it. We turned it off and don’t see anything, but when we turn it back on, it again clacks loudly. I’m fairly sure that it’s a blade-related problem even though I can’t see anything. Our repair company asked if we could last until morning and we said sure, as we have a fireplace and various electric heaters.

I’m not asking for professional advice, just opinions on what’s going on, and whether I might want to open the box or leave it for the expensive guys. Thanks.