Filed gstr3b for september month return but gstr1 of sept not filed

Filed gstr3b for September month but gstr1 still left to be filed.

Bcz I have added some missing invoices of last year in September month return.

So am I still eligble to add any missing invoices into gstr1 portal of September month whose last date is 31october ? 

Tax for all the months have been already paid in respective tax period every month..so no changes in gstr3b of any month

It's just that I have missed some invoices due to wrong gstnumber  in my records.