The "angel" could actually just be a projection of your own conscious, expressing to you that this was only a dream. There have been many situations where one has a dream that's so mundane and realistic that when they wake up, they aren't sure if it was a dream or not. Maybe your own mind was trying to express to you that this was not and will not be reality, so that when you woke up, you wouldn't question if you just saw the future, or that when the concert actually does take place, you don't question which parts were actually happening, or which were the dream.
Angels generally aren't fond of humans, and only give messages or visit humans when sent by God. If you generally believe it was an angel, and not your conscious talking to you, the question you need to ask is, "What message was God trying to give me." which means you need to go over every aspect of this dream and see what God was trying to show you.