Wrong GSTR3B because of IGST/SGST/CGST confusion, how to repair?

Hi,

I made a mistake when filing my GSTR3B for Aug 2020. I paid SGST+CGST rather than IGST. So, no tax evasion as such.

I file quarterly GSTR1. When trying to file GSTR1 for Sep 2020, I realized my mistake. I am yet to file GSTR1 for Sep 2020. I have filed GSTR3B for Sep 2020 (correctly). 

How should I repair my mistake?

1. I think I need to pay the Aug tax as IGST using a fresh new challan.

2. I do not want to claim any refund for SGST and CGST already paid. I will adjust that in coming months.

3. Will the system allow me to file GSTR1 with all the correct things, even though I have not paid IGST but declared IGST in GSTR1 now?

4. If I can file GSTR1 like this, at least my GSTR1 will be right. But how do I repair GSTR3B for Aug 2020?

5. If I cannot file GSTR1 like this, what should be the right sequence for me to correct my mistake?

Kindly advise.

Regards,
Ramesh