A couple issues here;
That grout is going to scuff your urethane, at best, when you try to remove it. You may need to have that area touched up by a pro.
Did that grout get on the wood because the grout meets up to the wood flooring directly, with no expansion gap? If so, you have another problem.
But, fixing Problem #2 may take care of Problem #1.
If your grout meets the wood; first remove it with a grout saw so you have an expansion gap.
If the tile is a little higher than the wood, get a reducer and flip it so the high side is to the ceramic.
If they're flush, get a t-moulding. If, after you have removed the grout, there is not enough of a gap for the leg of the t-moulding to fit in the gap and still leave a 1/4" gap between the wood and the leg of the t-moulding, the wood needs to be cut back a bit so that this can happen.
After removing the grout, possibly cutting back the wood just a bit, and installing the moulding, the area you're concerned about might get cut away or covered by the moulding. In that case, problem is solved.