Your age in a dream, if different than your current age, may represent a specific time frame you're thinking about or imagining in the dream.
Lying about your age may mean you wish that you were older or younger than you are, or at least appeared that way.
The age of another person may provide clues to who or what they represent in your real life. If you know the person, and their age in the dream is different than their real age, it may indicate that you think of them as younger (young at heart or immature) or older (more mature) than their actual age implies.