Deductions & credits

I made the mistake of not using 2019's earned income in order to calculate my qualified credits for 2020. I have already filed and I am set to receive a refund this week. However, my question is, am I able to amend in order to recalculate my earned income? Can I fix this small error through amending in order to get the qualified credits I am entitled to this year and every year? I was not aware of this stipulation until after I filed this year early this month. Please any information is helpful. @KathrynG3