GSTR 1 instead of GSTR 4 under composition scheme

please
help to solve the below issue:

I am registered under composition scheme of GST in month of August 17 and by mistake I raised GST invoice with 18% tax and I have purchase invoices also for input credit....
but now I want to file all the returns and pay the liability as per the regular tax payers from the beginning....
how to do the same.