Just don't ignore the extra one. That would be cruel.
'Wait, I only have two feet, so what the hell do I do with this third sock?' Well that's a good question, Mr. imaginary dude who we'd like to think is you. You can do number of things with it. For starters, you can wear it on your junk while you rock like a four-piece rock ensemble who's dear to us and to their fellow Californians. Otherwise, save the extra stocking from the Stance Three Of A Kind Skate Socks until you lose one in the dryer or just rotate it into your routine like a spare tire.