I forgot to change my w4 from married to single after my divorce. I am going to file single. Is this the correct thing to do? Also will it create issues down the line with the IRS?

The number of allowances and marital status you claim on a W-4 has no bearing on your tax return. It may cause too much or too little tax to be withheld during the year, but that is the only issue.

If you were no longer married on or before 12/31/2016, your filing status is single.