How is symbolism used in "A Little Cloud"?

Symbolism is used by Joyce to convey the general theme of "A Little Cloud" and the other stories in Dubliners: the restricted, provincial, suffocating nature of Irish life. The title of the story is itself symbolic. Little Chandler, in spite of his elevated ambitions of being a great poet, is just a little cloud in a much larger sky. He desperately wants to escape the stultifying boredom of his workaday existence but lacks the courage or ability to do so. So he floats along in life like a cloud, barely registering any kind of presence against the sky's expanse. A cloud can also symbolize the dreamy, hazy fantasy world that Chandler inhabits. His dreams of being a poet are precisely that; his head is permanently stuck in the clouds, unable to connect with the world around him.
Gallaher is also a symbolic figure, but at the same time incredibly real. In fact, he is considerably more real than Little Chandler. He is much more worldly, for one thing. Unlike his friend, Gallaher is actually living the dream, working as a successful journalist in London. He symbolizes the life that Chandler could have had if only he had the courage to take a chance and break free from Ireland.
Chandler's family could reasonably be seen as symbolic of Ireland at the time Joyce wrote the story. Home life is not a source of loving warmth for Chandler; it is a place of boredom, restriction, and lack of fulfillment. And the traditional Irish romanticizing of hearth and home has no appeal for Joyce, either. His eyes are firmly set upon being a great European writer, an artist of universal renown.
Chandler's poetry books gather dust on the shelf, unread, unloved, unappreciated. He wanted to read them to his wife, but he was always too shy to do so. Joyce too feels unappreciated by his fellow countrymen. But he is not too shy to bring his work to their critical attention. It is just that they would not understand it. His literary vision—so ambitious, so European, so un-Irish—is wasted on them.
The howls of derision and incomprehension that so often accompanied the reception of Joyce's work in Ireland are symbolically prefigured in the persistent bawling of Chandler's baby son. The child is too young to understand Chandler's poetic ambitions. And Ireland is too immature, too culturally insular, to appreciate the unique literary vision of James Joyce.