Well, you had a very good question. I was going to say that Satan’s sin would have been of a different sort as he was not created for fellowship with God in the way we are created, and that God gave the commandment to not partake to Adam alone.
So, yeah, I’d say there was sin in Satan before the sin of Adam and Eve occurred because Jesus tells us that Satan was a murderer from the beginning. But with that said, that we are to focus on the sin of man in relation to God.
(I hope to goodness you play chess, Seven!)