You need professional help since you are dealing with a closed tax year ... since you did not make the election to waive the carryback timely you MUST carry it back first and if there is anything left over then and only then can the remainder be carried forward to 2017. Same with 2017's NOL since it was not made timely.
Waiving the Carryback Period https://www.irs.gov/pub/irs-prior/p536--2016.pdf
You can choose not to carry back your NOL. If you make this choice, then you can use your
NOL only in the 20-year carryforward period. (This choice means you also choose not to
carry back any alternative tax NOL.) To make this choice, attach a statement to
your original return filed by the due date (including extensions) for the NOL year. This statement must show that you are choosing to waive the carryback period under section 172(b)(3).
