The setup. Oak floors sanded to perfection with 100 grit. Vacumed and tak clothed to remove any dust. Using a oil based expresso stain. Floors look perfect except in a few spots where sweat dropped onto unstained wood before the stain went on. I noticed and allowed time for these spots to dry before staining but the spot is still noticably darker then the rest of the floor. Can i hand sand that one spot? Any other fixes besides resanding the rntire room and waiting for a cool day? Any help is appreciated.

yes hand sand it out...use a rougher grit as it always works best for touch ups..

best to fix before sealing

When you apply the stain and it is fresh and still wet, after you have wiped off the excess, this is the color you will get after the stain has dried and a coat of solvent based finish is applied.
If there are any inconsistencies at this time, it is best to remedy them. Scraping dark spots or sanding scratches or machine marks before the stain dries will be the easiest repair. A sharp scraper to remove the problem and then using an 80 grit sandpaper to open the grain so it will match the sanding job should fix the
dark area and look fine after you re-apply the stain to the spot.
After the stain has dried with a dark area it makes it harder to blend in. We use old carpet, cut into skates to glide over the freshly stained area to check color consistency before the stain dries.
You can use sand paper to lighten the spots now, but they will show a little if you look for them.
Pete

IF there is one affected board, work on that one board.You can carefully blend the new stain into the flooring . Just take your time .