I understand your dilemma, but I would not usebondo (sorry Henry) or putty. It will never look right. I have been doing wood floors for a fewyears and I have two suggestions.
They are:1) Carefully pull up the old floor boards and reinstall the floor, tight the way you want it.and2) Put down new hardwood floors.
Both methods may seem extreme, but I truly believe that any other method will not look right.
I hope this is helpful.
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