You can't remove the excess after April 15. At this point, you must pay income tax on the excess deferral (add it back to your taxable income). Then when you retire, you will pay tax on all your withdrawals, even though a small portion was already taxed. That's just the way it works if you miss the deadline to withdraw the excess deferral.
If you paid tax on the excess deferral when you filed, then you don't need to do anything more.
If you did not pay tax on the excess deferral, you need to file an amended return to report the excess deferral as "other income" and pay the extra tax. While Turbotax can tell you that you have an excess deferral, it does not automatically add it to your income so you have to do that yourself.
