Nicodemus had just started complimenting God's work through Jesus, but Jesus started by making known his reason for coming (vs 3). I guess Nicodemus' question is "Rabbi, how can I be saved and enter the kingdom of God". But before he asked, Jesus hit the nail on the head.

If Jesus missed Nicodemus' intention for coming, he(Nicodemus) would have say something else in verse 4. And the fact that Jesus hit the target made the conversation to continue.

      Remember what Jesus told us in Matthew 6:8b "For you father in heaven knows the things you have need of before you ask him"(NKJV). But yet HE required of us to come (Matthew 7:7) and ask till our Joy is full (John 16:24).

      He always know your intention for coming (praying) but He want you to come and ask. please don't neglect the place of prayer. It's well