Someone pointed out the other day that the only time Jesus is directly addressed in the nominative κυριος as opposed to the vocative κυριε is in Thomas’ declaration, “My Lord and my God” (John 20:28, ο κυριος μου και ο θεος μου). Is there any significance?

Jesus is at the wedding at Cana, his mom sees a need, and asks Jesus (well, actually tells him) to help. Jesus’ response is,τι εμοι και σοι, γυναι; (Jn 2:4). Word for word, Jesus says, “What to me and to you, woman.”