"am I going to have to pay significantly more tax on the earnings"
When distributed, earnings in the traditional 401(k) are taxable as ordinary income whether or not they derived from excess contributions. If you have no after-tax basis in the 401(k), any distribution from the 401(k) is entirely includible in taxable income. Even though the excess contribution came from already-taxed money (due to having to report the excess contribution as miscellaneous taxable income on the tax return for the year in which the excess elective deferral was made), the excess contribution does not add to your after-tax basis in the plan.
If not already reported on your 2022 tax return, the excess contribution must be reported as miscellaneous taxable income by amending your 2022 tax return. There is no reason related to this to delay amending your 2022 tax return. You'll just want to wait until your 2022 tax return has been processed before amending.
