I just realized my employer did not include 3rd party sick leave in my w2 It may take time now should i file an amendment after filing taxes or ask for extension?

I would suggest file for an extension, but be sure to pay as much tax as you think you will owe. 

More is better than too little. 

If you file now, and then Amend, you most likely will owe additional tax and interest. Additionally, the IRS has to process 2 returns, which takes time.

You should file for an extension to file your taxes. However, you need to make sure to Pay an estimate of what takes you will owe by 4/18/2023 including both withholding and any additional from investments (if any).