It depends on who's name is on the 1099-MISC form. If it is under your name, then you need to report that on your tax return as "other income". This is not considered self-employment income, so you will not have to pay self-employment tax, but you won't be able to deduct any expenses. This income will be taxed as ordinary income.
If the 1099-MISC is in your child's name, see below.
At What Income Does a Minor Have to File an Income Tax Return?:
• A minor who may be claimed as a dependent must file a return if their income exceeds their standard deduction ($12,950 for tax year 2022).
Here is a link with more information: At What Income Does a Minor Have to File an Income Tax Return?
As far as 2021, IRS states you must report "other income" even if you didn't receive a tax form (1099-MISC in your case). If you need to Amend your 2021 tax return, follow this link for steps to Amend: How do I amend my federal tax return for a prior year?
