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.
Here's a clue...the Bible is God's word and its truth is something that is spiritually discerned. The "natural" man doesn't receive the things of God and he cannot even know them - he has no indwelling Holy Spirit who leads him to the truth. Another clue...the Bible is not written in some kind of "code" that only a magic decoder can interpret. I hold to the Biblical view that the words, in context, mean what they say.
There have ALWAYS been disputes over doctrines and since the start of the Christian communities, God has gifted to them through the Holy Spirit those who are able to teach and lead. Peter recognized Paul's writings to the churches as Divine in origin, he stated:
Those who are unlearned, ignorant and unstable stumble over God's word and it is usually the reason why there are disputes on the major tenets of the Christian faith. It takes study, prayer and a desire to know the deep things of God so that one may be able to give an answer to everyone that asks of the hope within us. Biblical hermeneutics is a study of Scripture using not only context but target audience, word meanings, customs, etc. to understand the things God's word teaches. Certainly Pastors, teachers, elders and others are gifted with not only the ability to understand the truths of the faith but be able to teach others so that the faith once delivered unto the saints is preserved and passed down.
When you ask, "Who gets to decide what the Scripture means under sola scriptura?", you miss the point of what sola Scriptura IS. The heresies that crept into the early churches were disputed BY Scripture. Athanasius of Alexandria, for example, disputed with the Gnostics and Docetists of his day who denied Jesus Christ was God in the flesh. He had the better argument from Scripture and helped to formulate creeds that outlined the Apostolic doctrines as they had been taught through the written word. I hope you would agree that there cannot be diametrically opposite doctrines that can be proved through the Divine word. There is only the truth - and that truth IS spelled out for us in God's word. The Apostolic letters were meant to do that spelling out. Spiritually gifted teachers - those who put in the work - are able to teach others also. Because God's word is powerful and able to make one wise unto salvation, is why Scripture, alone, is the authority over and above any human.