The aerator on my bathroom faucet gets dirty, so I've been cleaning it out now and again by rubbing a paper towel around the bottom. I think I did this with too much force, because the plastic interior snapped right off.
Apparently you can unscrew an aerator and replace it, but this is my landlord's sink, so I just want to be sure what part to unscrew. I've attached images of the sink and the piece of the aerator that snapped off. Any ideas?