The amount my former employer entered in the W-2 form's Box 16 (State wages) is wrong, but they're not going to fix it. How should I report the correct amount?

The employer no longer works in my state, so they don't have employees knowledgeable on what income is taxable here.  Should I just enter in TurboTax the amount I know it is supposed to be, or is there a different place to enter a correction?