Repairing dents in wood floors

Q: We recently moving into an old historic home. We placed felt protectors or coasters made to protect wood flooring on all of our furniture. I have discovered some dents in the wood when cleaning the floors. Is there a way to repair these places?

We are renting and I am quite concerned about this!

A: I have heard of, but have never tried this: dampen a cloth, place it over the dent and heat it with an iron. The theory is to cause the wood fibres to expand.