Invoice shown as unregistered and tax also paid under wrong head

you can amend in next month gstr1 in table B2Csa by reducing the amount which u wrongly show in gstr1


step1 : select b2csa , month in which you wrongly show, select state on which you added b2c in previous month
put value after deducted the wrong value
step 2 show B2b value in B2B TABLE WHICH YOU ARE WRONLY ENTERED IN PREVIOUS MONTH

But what about the tax paid as tax was paid under Sgst and Cgst instead of Igst.

reverse in subsequent month return.by reporting net liability after adjusting the mistake of previous Month