I live in a basement apartment and i tried to fix a leaking shower and failed. But now the water pressure in my kitchen is low.

These issues are problably unrelated but we'll see. Lets start by removing the aerartor to see if the pressure improves, if not we can start with the valve. Back to you.

Yes I removed the aerartor and cleaned it. But the pressure is still very low. The pressure was fine until I fixed a clog in the bathroom sink and tried to fix the shower.

Still thinking unrelated but the jury is out. Next thing to do is one of 2 things. We need to remove the mixing valve to see if its clogged, slightly difficult . #2 you could open the supply lines at the stops under the sink and test for good pressure there, easy work but the first approach is what a plumber would do.

I checked the supply lines. How do I remove the mixing valve and what is it?

There may by dirt in the cartridge of your sink faucet. Post the make / brand of your faucet and we will tell you how to proceed with removing its cartridge.

As stated several times before by others, your plumbing problems are not related.

OK but how about a few details about how you checked your supply lines. Did you remove the line before or after the stop? How much volume and pressure was there? If both volume and pressure are good then it is likely the cartridge like Milo said, I was going there in my 4th post. Tell us about your faucet, details like brand and model if you can get that info.