1′ x 1′ Area where the wood is white.. or lacking stain

Q: I recently bought a 107 year old house. Upon ripping up the carpet I discovered beautiful, finished hardwood flooring. However, it seems (also told to me by seller) that the previous tenants (was a rental) had a dog (were not suppose to) and by the smell and sight, this dog went wee in the house.

There is a 1′ x 1′ area where the wood is white or lacking stain. Is this perhaps caused from the acid in the urine and soaking through? This is in the spare room, but I fear finding more of these spots, as this is a 2,200 sq. ft. home and mostly carpeted.

How should I approach this? Should I clean the floors first and restain? Clean and cover it with a rug? Only kidding. It also seems this house has had carpet for the last 21 years while in hands of last owner. He took GREAT care of this beauty, phew. Just need help with how to approach cleaning these poor suffocated wood floors. Thank you, in advance, for any help you may be able to lend.

A: Uric acid always makes the wood go black, not white. Black spots? You might have to change the boards.