Input taken as cgst sgst instead of IGST

Please refer Circular no. 26/26/2017 dated 29 Dec 2017 for the detailed procedure for this case.

further, you can pay(through cash) / Reverse any wrongly reported input tax credit in return of
subsequent month(s).

For under reported input tax credit, the same
may be availed in return of subsequent
month(s).

Yes... I agreed to Mr Surjeet Negi.

Advisable to revise/pay the excess claimed ITC and show the missed ITC as per Your regular practice...

No need to pay ..... if there is no tax liability.

Reverse the same under CGST/SGST & Claim the same In IGST in your Next GSTR 3B .

Yes if You have paid the Tax in CGST/SGST instead of IGST , Then as per Section 77 of CGST need to pay tax In IGST & can claim Refund for wrong paid under CGST/SGST .