Issues with my fan

Hey, so I know very little about computers and my laptop was turning on for a bit then turning off. So I opened it up and did a bit of a (much needed) dust clean.

After reassembling, I turned my laptop on and the fan is whirring very fast/screeching, entirely dependent on how the laptop sits. It varies, but either way it’s incredibly loud. And I’m really really concerned.

Nothing seems broken, I’ve inspected what I can get at without dismantling everything and the fan itself is fine. When I spin it with my finger to test it, it glides smooth and doesn’t screech, and there’s nothing to say it’s rubbing against anything. I’m very perplexed.