It depends if you itemized your deductions or took the Standard Deduction on your return.  If you itemized, then the Mortgage Interest may increase the total of your itemized deductions and reduce the amount of taxes due and/or increase your refund. 

But, if your tax return used the Standard Deduction, then including your mortgage interest would not have any impact on your return. 

To see if you used the standard or the itemized on your return, look at line 8 of your 2018 1040 form.  The standard deduction amount is $12,000 for singles or married filing separately, $18,000 for head of household, and $24,000 for married filing joint, plus additional for over 65 or blind.

If you feel you need to amend (to record the mortgage interest), here is a link that will be updated with steps to amend once the 2018 amendment tax form (Form 1040X) is available.

https://ttlc.intuit.com/replies/3288565