If you have not mailed or e-filed your income tax return, sign into TurboTax and correct your son's social security number in the Personal Info section.
If you've already mailed or e-filed your income tax return, you won't be able to change it. It's like putting a letter in the mailbox. You can't retrieve it. You'll have to wait until the IRS processes your return. The IRS has announced that they will begin accepting and processing 2020 individual tax returns on February 12, 2021.
If your return gets rejected, you'll be able to correct the SSN and submit the corrected return.