Here, the psalmist expresses and sings praises to the omnipotence, omnipresence and omniscence of God. God was involved in every detail of our creation He offers us a view of God personally weaving (stitching) every inch of us in a way that reflects care about the outcome of us as his creation. The imagery he uses is intended to show the great amount of thought and attention to every minute detail that God has put into our creation. God left nothing to chance. Because he has discerned how much God loves us he asks for retribution against those evil ones who refuse to acknowledge the glory and majesty of God.
But, in the end, the psalmist pointedly asks God to search him, the very being that he knows God already knows intimately. He then goes further by seeking God's correction if he finds any unseemly thing in him.