If the stain is a whitish blushing created by entrained moisture in the finish, placing a cotton cloth on the surface and using a hot clothes iron on the cloth draws the moisture out of the finish restoring the clarity. It's a standard method used with water stains on furniture and other wood objects with applied finishes.
Radio controlled model airplane builders use a small flat iron to apply and shrink covering (Coverite) over the structures of the airplanes they build. They have a small footprint and can get hot enough to do the above and won't heat too large an area like a regular clothes iron footprint will.
Search for Coverite or TopFlight iron. You can find them as low as $20.00 or less.