Sometimes you forget and fall behind, and you just need to catch up so you can keep playing. The fix scores view allows you to change any of the set or game scores by tapping on it. (You can tap on a set or a game score to edit it.) Rotate the crown to change to the correct score, then hit the "Resume Play" button which puts you right back into the scoring view.
Use crown to dial in the correct score, then tap Resume Play to get back in the game.