if the remaining floor has not been sanded and looks alittle rough, sanding in this spot will show up more than the accident itself.
What I would do is to make sure that the leak is fixed and the area is dried out thoroughly.
The water has caused the grains in the wood area to swell and crack.
I would sand down the area smooth, progressing from course to extra fine. Then add a sand sealer to cause uniform stain. Then the water in this sealer will again cause the grain to swell so you will need to lightly sand again.
Then stain the area with the same stain, then seal it. This should work.
You might want to feather out all the edges for a blended look and the same with the stain and finish coat.
also, blow out all the saw dust in the cracks. When you seal and stain this could be permenant and affect its movement.