Oh no.  Well, now you just have to wait.  The IRS will not even begin to accept or reject 2018 returns until January 28.  Since you e-filed it, it is just sitting on a server, and you cannot do one thing to fix your mistake.  You cannot cancel it, stop it, or change it.

If you get lucky and they reject your return, you will be able to correct your mistake and re-submit it with the correct W-2.  If it is accepted, then your real wait begins.  You will have to wait until it is fully processed--which will take at least a month, then you will have to prepare an amended return called a 1040X which you print, sign and mail to the IRS.  It cannot be e-filed.  It takes the IRS about 4 months to process an amended return.  IF you are getting a refund from that amended return, they will mail a check (no direct deposits for amended returns).

Meanwhile, do NOT try to change anything on your tax return.  If you do, you will make a big mess for yourself and it will be even harder to sort out.  Sit tight and see what the IRS does with your return in a few weeks.  Post back here for help when you know whether it was accepted or rejected.  You will get an email after January 28 telling you if your return was accepted or rejected.

We will help you.