When the water pressure is low in just one sink, it is usually a clogged aerator. If you are not careful about laying down the small pieces inside the aerator in order, you may have trouble getting them back in. If they don't go back in the way they came out, the aerator will not work properly. It only takes a few minutes to reassemble the aerator. They are all different, however, so you may have to experiment with a couple of pieces. This article will explain how to reassemble a faucet aerator.
Hold the metal cap that screws on to the faucet in your hand. Place in the metal screen so the screen part shows through the bottom.
Next, slip in the plastic piece or pieces. There may be a plastic screen and a plastic piece that mixes the air into the water. If you have both, the plastic screen will go next and then the piece that mixes air into the water. If you only have one plastic piece, it goes in now.
Lastly, place the rubber washer in and screw the aerator back on to the faucet. You should be able to tighten it by hand, but if you have water dripping out the sides you will need a pair of pliers. Wrap the teeth of the pliers in duct tape before using them on the chrome piece or they will scratch it. Do not overtighten or you can dent the chrome and strip the threads.