If you didn't take out the trash, more American English here in the UK, we say rubbish, not trash. When you noticed I'd done your chores, you felt so bad that you'd do some of mine to make it up. If you make it up to someone, it means you do something to kind of compensate them or to repair something. Like in this case, she did something for him. And so he feels like he should do something in return to compensate her for what she did. To make it up for him. We tend to use housework but chores is nice word.