When did the application arrive at USCIS? What is the priority date? If it arrived at USCIS on or after the 90th day, and the priority date reflects that, you should be OK even if it was mailed at 91 or 92 days before your GC anniversary.
While we warn against mailing or signing it before 90 days, that is to protect yourself from USCIS mistakenly rejecting it without an interview due to them (wrongly) looking at the postmark date or signature date. If they do their job correctly they're still supposed to process the application if it arrives on or after the 90-day mark, even if it was postmarked before that.