This puzzle is a rebus - one of the squares requires more than one letter. To enter more than one letter, select the square and hit 'esc' if you're on the computer, or the three dots in the corner if you're on a phone.
Expression after a mistake (6) [WHOOPS] haha I fixed it. I need to either stay in my lane for pop culture I clue, or take the time to check google I guess lol. Thank you!