After you file

The way to fix this is to amend the return that the original 1099-DIV was reported on. 

Per How do I amend my federal tax return for a prior year?, here is how to file an amended return in TurboTax Online:

1. "On the Tax Home screen, scroll down to Your tax returns & documents and select the year you want to amend.
2. Select the Amend (change) return dropdown, then Amend using TurboTax Online. If you're told to amend your return via TurboTax Desktop, follow the steps for TurboTax Desktop instead.
3. Continue through the screens, make the changes you need to make, and carefully answer the remaining questions to finish amending your return."