Unfortunately,
you'll need to amend your return.
Please see the
TurboTax FAQ "How to amend (change or
correct) a return you already filed," below, for instruction on how
to amend your previously-filed tax return.
Please
note, however, that Form 1040X, the Amended Return form you need, isn't yet
available for filing. The tentative
availability date for Form 1040X is 02/22/2019.
https://ttlc.intuit.com/replies/3288565
