I installed a new faucet and drain pipe assembly. I found that there's a small hole at the bottom of the sink (underneath). Water is coming out of it. When I pull up the stopper (so the water collects inside the sink), there's no leakage. But as soon as open the stopper or open the faucet, water is start dripping through this hole.
Anyone knows why is it here, why is it leaking, and how could I fix it? There didn't seem to have a cover or "plug" for it previously.