I wouldn't stress out over it. It may warrant a brief
addendum - but it won't break your app. This is a very minor flaw... if you were expelled, that's a major flaw... withdrawing from a course your first semester... please. Everyone, including those that get accepted to these top schools, has something in their app that isn't perfect. Which makes sense... we are all human. The difference in those who get accepted v those who don't is probably the way they present those flaws. Do they talk down about themselves? Do they disrespectfully and smugly shrug it off? Or do they accept it and use it as a vehicle to learn from - to grow. Go for the latter.
Good luck! And congrats on your high academic achievements thus far.