Can I file the Recovery Rebate Credit form separately if I have already filed my 2020 taxes? Learned too late that I had to fill this form since I didn't receive my $600

I was expecting a stimulus check for the $600 but didn't receive it...I went online and found out I had to fill the Recovery Rebate Credit when I filled my 2020 taxes. I learned too late of this and I have already filed my tax return. What are my options?