ITC wrongly taken as CGST&SGST instead of IGST

Hi, 

On April 2019, I bought service & got IGST around 3500 but I had taken this as CGST & SGST in both (7000 in total). Since I sell most exempted products I had reversed 80% under section 42&43. So basically ITC available was around 700 in IGST but taken as 700 in CGST & SGST ie 700 taken in excess. 

How I should rectify this situation or how to reverse the amount. I still have some amount credit ledger. 

Thanks in advance.