Yes you should report

If you used TurboTax last year and transferred last year's income tax return into this year's income tax return that loss has already been included in your 2016 income tax return and shouldn't be reported again.

Since this is 2017, I think you mean you sold stock at a loss in 2016 and received a 1099-B for 2016.

If that is the case you enter the 1099-B information and report the loss, which will be used to offset some of your other income.If the loss is great enough, any losses remaining will be carried over to 2017.