Hi Ed, sorry you have dark stains on your hardwood floor. I hope this will help you. How to Remove Dark Water Stains From Hardwood Floors
How to Remove Dark Water Stains From Hardwood Floors | Hunker
I suggest you take a good picture to your big box home improvement store. Show a manager the photo and see what suggestions are offered up. They are experts in this department. Also you can try a local craftsman that refinishes furniture. He may be able to correct this for you for a fee or may even tell you how to correct it yourself.
Hi Ed: You can try rubbing some Vaseline.
Clean the floor if necessary, and get a rag and dip it is the Vaseline and rub a goodly amount into the wood where the damage is.
Let it stand for an hour or so. It pretty much works right away, but leaving it on for a little bit doen't hurt.
Wipe excess of with another rag. Some petroleum jelly residue will remain.
Come back later and wipe it again to get all of the petroleum jelly off.
That should work for you. Good luck
Sand them that’s it