City replaced water meter, then bathroom sink pressure dropped, rusty water
You're right--some metal was jarred loose by the work on the meter and the resulting pressure shock. What you weren't able to clear out already is probably stuck in the aerator screen (or flow reduction disk, if present). 

Unscrew the cap at the faucet outlet. There should be a mesh screen there, and possibly a perforated plastic disk. Pull them out and rinse them. Run some water through the faucet without the screen and disk. 

If that doesn't clear it up you'll probably need to disassemble the faucet. That's not usually difficult, but may involve replacing some o-rings or seal seats. Most faucets made in the last 15-20 years will have replacement parts available at hardware stores.