Getting a water stain out of wood

One of our children spilled water on a wood nightstand and the water ran under the glass top that is there to protect to wood. The water stayed trapped between the glass and the wood. We have no idea how long it sat. Cool air from a hair dryer has helped but has not remedied the situation. Online has different suggestions form Mayo to a warm iron on a microfiber cloth and mixing oil and vinegar. Any suggestions or experiences with these different remedies? Thanks!