The stain described is most likely a water stain in the finish (cloudy haze), if it is go to the hardware store and purchase some rottenstone. Make a paste like toothpaste with baby oil and rub out the spot with the grain of the wood. Clean the compound off and wipe dry, if the stain is still there try again....be careful not to go thru the finish.
If the White stain is raised the finish may have popped and will need to be redone.
If the finish has a dark ring under it, the top will have to be redone.
If you are unsure that you can do this call in someone who repairs office furniture.