Help please - water leak, discolored oak floor

Came back from the beach last night and found a leak at the powder room toilet. Water standing on the hardwood flooring. Mopped it up and fans on to dry, but there is a black discoloration at parts of the floor now.

Any tips on how to remove the discoloration? It is darkish, blackish.

Floor is red oak, stained with MinWax Golden Oak, with MinWax Poly as topcoat.

Thanks for any assistance in advance! jim

Oxalic acid might take it out. I bought mine at the grocery store (Kroger) labeled as "Bartender's Helper" or "Bartender's Keeper". Make a thick paste, like peanut butter. Spread it on. Leave it until dry. Brush away, hopefully the stain goes with it. This technique worked perfect for me taking metal stains from wet loose nails out of bare red oak.

Bob