I don't think you understand what the doctrine of sola Scriptura means. What it doesn't mean is SOLO or ONLY Scripture can be used to know the truth. Because Scripture, as the sole Divinely-inspired word of God, is the superior and ultimate authority and determiner of the truth of the rule of faith. It means that Scripture is the measuring rod by which any doctrine must be held to. It cannot go against what God has said. Paul taught, "Do not go beyond what is written. Then you will not be puffed up in being a follower of one of us over against the other." (I Cor. 4:6). That is sola Scriptura.
Well, since nowhere in the 27 books that make up the New Testament canon of Scripture is there a list that authenticates them to be inspired, their legitimacy cannot be distinguished with certainty except by some other infallible source.
Here, I'll answer the question for you: you decide what it means for you, and only you decide, in the final analysis. There is no possible authoritative interpreter beyond the individual. That is what Luther demanded when he said "Hier stehe ich, ich kann nicht anders!" And he was shocked -- shocked, I tell you -- to discover that then other people insisted on interpreting the Scriptures for themselves, entirely apart from what he thought those Scriptures meant. Unforeseen consequences and all that ...
And so the atomization of Christianity began.