You could apply some fungicidal treatment, my guess is it will disappear and never come back if the wood remains dry.
I don't know the name of the fungus, but I am sure its easy to find either by googling using the pictures function or a decent fungas web site.
I have seen it many times though in real life and it only seems to be around really wet surfaces, normally timber
Its a type of elf cup fungus or similar, usually dies off once you get rid of the source of damp and does not usually require treatment as it only grows in excessively damp conditions and can't survive without the moisture.
Clear up the fungus, dry out the floor and when dry apply some fungicidal fluid for timber just for peace of mind.
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