Now you wait for your own return to be fully processed and you amend it to change the way you answered that question in MY INFO that asked if you can be claimed as someone else's dependent. Do not try to change anything on your return yet. You cannot amend yet. You need Form 1040X which will not be available for at least a week.
But your parents do not need to wait for you to amend. They have now been blocked from e-filing their return that claims you for the year----the only way they can file their return now is by mail. They have to print, sign and date their return in ink, and mail it to the IRS ---and state if you have a state income tax. Even if you amend your return----your parents have to file by mail this year.