Too late for this, but in future, a whole cup weighs 120 grams. So 12 grams isn't much.
You could just add a TBL of regular flour. It's when you have to substitute cup for cup that adjustments need to be made: usually, remove 2 TBL of regular flour from 1 Cup and replace with 2 TBL of corn starch.
For your small amount, it's no big deal.