What if I get another w2 for 2017 but already filed? Did not expect another one.

If you have already filed your tax return and you receive additional tax forms you need to file an Amended return, (1040X) once your return has been accepted by the IRS. However, the IRS is still working on finishing up the Amended Return forms. TurboTax expect the process to be ready on 02/01/2018 for the 2017 tax year. Once it becomes available you will need to send in any forms that caused the need for an amendment (original 1040 Form, new 1040X Form and your W-2). Then, print, sign and mail in your forms to the IRS.

It probably will take anywhere from 8-12 weeks for the IRS to process your amended return (once it's received). You may have to amend your state return as well, if it has caused a change. Please see FAQ, for more information regarding amending a tax return: https://ttlc.intuit.com/replies/3288565

IF you do need to amend, I would wait until 1 March to do it.  You may get some other forms during February, and amending twice is a nightmare that even we, who have been using and advising TTX users for years, have trouble figuring out.