Recently, I dropped a jar of pickles on my engineered hardwood floors. I cleaned it up immediately with a little Mr. Clean and water on a paper towel. It was still sticky and I used vinegar and water on a paper towel and then a little soap and water on a paper towel. The shine is still there but the finish is not the same. When you walk over it with socks, you don't glide over it like you do elsewhere. You can not see the difference, you can only feel it. What can I do to make the floor smooth again on that spot?
Before you do all of that, or considering you asked back in August (my apologies) hopefully this helps the next person.
Try floor wax first. If it APPEARS fine you don't need to refinish the floors.
Rub it on, buff it off, viola the floor is slippery again.
The finish was dulled by either the pickle juice, or because you used vinegar, both of which are acidic. Vinegar and water are good for cleaning some things, but will damage most floor finishes.
As suggested by @BrownRedHawk, you need to apply a new finish. You could probably try treating just that area with an acrylic urethane floor finish designed for laminates, but doing the entire floor will ensure uniform "feel" and appearance. These finishes are usually applied with an applicator pad on a stick. Try a good hardware store or flooring shop and don't buy the cheapest stuff.
How big of a spot? If it's an engineered floor, and you can find out the brand, it might be easier just to buy a new box and replace that spot.
Or, to save a bit more money, just disassemble the floor, and rearrange the pieces. You'll still have a few boards that don't 'feel' the same, but at least they will be spread out and not feel like this 'one spot' and more just natural variance between boards.