If you have already e-filed or mailed the return, you will need to wait until the IRS has accepted the return. Once they accept it and you have received your refund, then you can amend it. If it gets rejected, you can just make the needed changes and file again.
NOTE: The amend form will be ready for you in mid-February. Check back at this time if you would like to amend your 2016 return. Once amend form is ready, you can go here https://ttlc.intuit.com/questions/1894381 and get instructions for amending that return
See reasons why you'd need to amend below:
https://ttlc.intuit.com/replies/3318732