If your 2016 tax return did not report the resulting traditional IRA contribution for 2016, either on Form 1040 line 32 or Form 1040A line 17 as a deduction, or on Form 8606 as a nondeductible traditional IRA contribution, yes, you need to amend. While it might be possible to file just the Form 8606, including Form 1040X gives you way to confirm that there is no change to your 2016 tax liability and gives you a place to put your explanation.
