Can I go back two years and claim ctc if in self employed?

If you were self-employed 2 years ago and were eligible for the child tax credit and did not claim it, then yes, you can amend your return to claim the credit.  This Child Tax Credit for the last several years other than 2021 was a non-refundable credit that would reduce your tax liability but is not refundable.  You may qualify for the Additional Child Tax Credit if you did not get the full Child Tax Credit. This credit is worth up to 15% of your earned income (self-employment is earned income) minus $2,500. 

In order to claim the credit, you would have to have an eligible child.  If you did have one and listed them on your return and used TurboTax, you would likely have received whichever credit you were eligible for.  However, if the child was left off of your return, you can amend to add them as long as they did qualify as your eligible child and no one else claimed them. 

You can go back and look at your return from 2020 and see if you have any credits listed on line 19 or 28.  If you do, then you already received the credit and would not need to amend. 

The rules for 2021 were different.  The credit was higher and many people got a check or deposit ahead of the filing season for the credit if they claimed the child in 2020.  Again, only one person can claim a child so if someone else claimed them, that person would have received the credit.