Isaiah 45:11-12. ” Thus saith the Lord, the Holy One of Israel, and his Maker, Ask Me of things to come concerning My sons, and concerning the work of My hands command ye me. I have made the earth, and created man upon it: I, even My hands, have stretched out the heavens, and all their host have I commanded.”
God is often referred to in Isaiah as The Holy One of Israel. This is an important title, and indicates One Who can do no wrong; One Who is beyond our understanding in holiness and righteousness; and One Who cannot be questioned in a presumptuous manner.
He is the One Who knows of things to come concerning His sons (Israel); He created Israel, and He knows their future.
God is not boasting in verse 12. He is simply stating the truth, and impressing upon all mankind that He alone is God, and there is no other.