Dampen one corner of a clean cloth with some mineral spirits. Rub firmly in a circular motion over the stained area in small sections at a time, being careful not to saturate the wood. If the stain is light, the mineral spirits should clear the stain away.  Mineral spirits is a solvent commonly used for paint thinning. It is readily available at hardware stores. Mineral spirits is very strong and can cause skin irritation, so be sure to ventilate the room, wear rubber gloves and be very careful in this step.  If the stain is particularly stubborn, you may need to repeat this step a few times. Using a clean cloth, wipe off the mineral spirits with a solution of detergent and warm water, rinse with clean water, and then dry with a cloth or towel. When the wood is dry you will be able to tell if you have removed the stain. If the mineral spirits have not done the job, you may need to repeat these steps. Once the surface is dry and the stain has been removed, it’s a good idea to polish the wood to restore its luster. Apply wood polish sparingly with a soft cloth. Rub in a circular motion until all the polish is absorbed by the wood.

Summary:
Apply mineral spirits to the stain. Wash off the mineral spirits with detergent, and pat dry. Allow the wood to dry completely. Polish the wood with a soft cloth.