My Dermatologist Told Me I Have Bacteria Under One Of

My dermatologist told me I have bacteria under one of my finger nails and that I should soak it in diluted vinegar for 5 minutes each night. The dilution is 3T of vinegar to one quart of water. 2 questions - is it necessary for me to change the water each day? I see the same white under the nails in two fingers on my other hand. My other fingers were painted at the appointment so the dr did not see them.