I accidentally put i was single insead of head of house hold how can i change this after filing

Once a tax return has been filed it cannot be changed, canceled or retrieved

You will have to wait for the IRS to start accepting or rejecting 2020 tax returns on February 12, 2021
If the return is rejected you can make the necessary changes and e-file again.
If the return is accepted you will have to amend your original tax return. An amended return, Form 1040X, can only be printed and mailed to the IRS if the original return was not e-filed. The IRS will take up to 16 weeks or longer to process an amended tax return.

Before starting to amend the tax return, wait for the tax refund to be received or the taxes due to be paid and processed by the IRS.

See this TurboTax support FAQ on amending a tax return originally completed and filed using the 2020 TurboTax online editions - https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-turbotax-online-return/01/27577

If you were eligible for Head of Household, the program would have selected that filing status for you when you were in the My Info section of the program entering your personal information and the information for your dependent.

Are you qualified for Head of Household - https://ttlc.intuit.com/community/family/help/do-i-qualify-for-head-of-household/00/25539