The bible says nothing about the Big Bang simply because the people who wrote it had no idea about the Big Bang theory (or much of our science for that matter).
But does this mean that the bible is wrong to talk about creation the way it does? The answer is no. The people who wrote Genesis 1 and 2 wrote about how the universe came to be in terms that they knew and understood at the time. Had they been 21st century scientists they may have used terms like “Big Bang” and cosmology. Nor were they writing to answer the question of how the universe came to be but why the universe is the way it is.
From Genesis 1 to 3 we learn a great deal about who God is, about who humanity is in relation to God and the rest of the universe and why there is such a mixture of good and bad in the world. Genesis 1 shows us that whatever way the cosmos came into being, God was the one who was the active agent doing the work. It shows he is a powerful God able to bring the cosmos into being with a word. It also show that humanity shares a special place in the cosmos as the only creature who has “the image of God” and because of that we are special in God’s eyes. Genesis 2 shows us that we have been given responsibility over the cosmos, to rule it and use it but only under God’s authority. Genesis 3, however, shows how humanity rebelled against God and the consequesnces of that.
What Genesis does not show is scientifically how the universe came into being. If the Big Bang theory is indeed right, then I would be quite happy to speak of God actively creating the universe through the process of the Big Bang. They are not contradictory.
I hope this helps you in your understanding. For more information have a look at: