You are okay.
If you haven't attempted that performance tip where you can reset your timing over what was set at the factory (based on the use of lesser-grade octanes), there will be no harm done.
Plus, I find that when I'm stuck in a rural area for an extended period, sometimes I can't get much better than 87 or so...and I'm NOT puttin in that "gasahol" or whatever them "corn-squeezins" mixture is!
