It is indeed too late to just correct that return, unfortunately, You will now have to file an amended return. Wait until you're received the refund or your tax paid has been processed, before you do the amendment. DO not make any changes to your return until you start the amend process.
Amended returns are processed separately, they don't "catch up" to your original and correct it in any way. It can take the IRS up to 16 weeks to process an amended return and they have to be filed on paper in the mail. The 1040X that you use is not yet available but here are instructions for when it is:
https://ttlc.intuit.com/replies/3288565
