I have heard you can ad some water to the gouge ,let it absorb and swell a bit...and iron (with a conventional electric clothes iron) a gouge out. true or false?

If it is dented and the wood fibers aren't broken, it will work on raw wood. Not sure on sealed flooring. You can try it, but use wet rag with the iron.

but..................
don't try it if its an oiled floor or youll get a white spot......

If the floor is urethane coated, it isnt going to work.
If you have a diabetic in the family, you could try using an old hypodermic to inject the water through the urethane