Hi, Mary. You will need a damp washcloth or towel and your hand iron. You have crushed the fibers in the wood and you want to expand them again. We are going to use steam/water vapor to do it. Put the damp cloth over the dent and go over that with the hot iron. The steam will go through the finish and into the wood to expand the fibers. Check how you are doing every couple of minutes and keep the iron moving. You don't want to run the hot iron over a totally dry cloth or keep it in one place too long.
When you have brought the wood back to level or as close as you can get it, you may have some white blushing in the finish of the wood. If you do, put petroleum jelly (like Vaseline) on the spot and leave it for 24 hours. Mark the spot so somebody doesn't walk on it and slip.