Hello everyone, My question is about my bathroom sink, which won't stop running. I tried to tighten the knob which work for a minute. But the sound of dripping water came back after a few days. What do I do for this problem... Thanks in advance.

Below the sink, there is a shut-off valve to the faucet fixture. It should appear to go the knob in question. Turn it off. Remove the knob to allow access to the guts of the water valve. Remove the valve stem to discover the washer on the bottom of the stem. It is probably damaged. Assorted washer kits are available at all hardware store. Replace the washer; re-install the stem; re-install the knob and then turn the shut-off valve on.

What make and model is your faucet. How old. If you have a washer/seat valve then go with bones suggestion. However, you may have a worn seat, this can get a little more involved. Let us know what you find.