Did you include the 1099Misc income in your return when you filed? You needed to report all your income whether or not you got the 1099Misc. If you did not report that income you need to amend to add it.
How to Amend
https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-turbotax-online-return/00/27577
The IRS message means if you forgot to attach the W2 or 1099 if you mailed your return.
