Yes, you can amend your tax return to add your Form 1098. But, you only need to do that if you itemized deductions on the tax return you already filed, or if adding the mortgage interest makes your Itemized Deduction exceed your Standard Deduction. Otherwise, you don't need to amend your return.
For 2019, single taxpayers and married taxpayers who file separate returns can claim a $12,200 standard deduction. Married couples filing jointly can claim an amount that's twice as large, $24,400, and taxpayers filing as "head of household" (single individuals with dependents) can claim a standard deduction of $18,350.
Check the return you filed to see if it includes a Schedule A, Itemized Deductions. If not, your Line 9 on Form 1040 will be the Standard Deduction for your filing status.