I noticed a square foot of a dark stain on the hardwood floor in the living room. The floors are many years old in this rental and there is no gloss on them so I'm guessing they're unsealed.

I think the stain came from the dog's urine although I have no idea if it did. I think it's been there for quite a while.

Any advice on how to get rid of it without sanding the floors?

Also, how should I clean these floors. I'm afraid to put any liquid on them.