According to the Dartmouth Writing Program this is what you should do:
What happens when you've put your thoughts in a nutshell and they seem too "small"? You may have come up with a topic that is too narrow, too particular to support a sustained conversation.
Say, for example, that you've noticed that a novelist likes to talk about lipstick. He describes his characters as they put on lipstick. He allows his characters to leave lipstick stains on glasses. He talks about different shades of lipstick and how they reflect different moods.
You've collected some passages from the novel, and you think that you can write an essay that chronicles the use of lipstick as a metaphor in this story. But it's not enough simply to chronicle the appearance of lipstick in the novel - first it appears in chapter one, then it appears in chapter four, and so on. Instead, you have to make some declaration about what this recurring image means.
After writing your discovery draft, you come up with the idea that the writer uses lipstick to call attention to the fact that the characters are trying to mask their feelings. While this observation is a promising one, it still isn't "big" enough. Why not? Because it remains an observation, not an argument; it lists howA and B and C mask their feelings without addressing the matter of whythis masking is important to consider. How do you broaden your topic so that you feel that you have something important to say?
All of these questions might help you to broaden your topic so that your discussion is substantial and interesting.