If you did not actually withdraw money from your retirement account in 2016, then you can't correct the error using your tax return.

You are required to withdraw an RMD by April 1 following the year you turn 70 1/2 in order to avoid a penalty. Because you turned 70 1/2 in 2016, your withdrawal in March of 2017 is timely, and there will be no penalty.

If you intended to make the withdrawal in 2016 in order to lower your taxes, it's too late to make that change. You must withdraw a second RMD by December 31, 2017, and every year thereafter.