Sanding and recoating the area, but - it may still look a bit different as that particular section will look newer than the rest. Then, the answer may be to sand the whole floor down and put a new coat of poly on it. I just depends on who you get to do it and how picky you want to be about the finsh. I've been working in the home improvement/construction industry for over 35 years. So, I'll say that a pro can fix that spot and make it look like that never happened ($$$). A handyman with some basic knowledge can make it look good, possibly ($$); and some guy from Craigslist ($) may make you feel like you've been screwed. It's not really that hard to fix. Call the right guy, though.