GSTR3B filed but not GSTR1

Sir
I have started my own proprietor ship last year and registered on GST portal as advised by the bank in order to open a current account. Soon I received SMS that GSTR3B not filed then I logged in the portal and filed GSTR3B NIL return because 0 students have been admitted in my tuition centre business. That filing of NIL return for GSTR3B I continued till now but the issue is that now I am unable to file annual return because the system is saying gstr1 not filed. But all these months I never received any sms for gstr1 and neither I faced any problem in filing NIL return for gstr3B. Now what is this gstr1? how to file it because now system is saying “validated but not filed” and how to file gst annual return?