I think that one significant symbol in the story is the presence of written correspondence. The story opens with Nnaemeka hesitating to write a letter to his father about his impending marriage to Nene. Writing a letter is the initial conversation about Nene and Nnaemeka about their marriage, the ways of the Ibo, and the clash between their love and tradition. The writing of a letter serves to establish the basic trajectory of the work.
Once it becomes evident to Okeke that his marital wishes for his son are not going to be met, he communicates only through written format. His letters are terse and bordering on cruel. He sends back the wedding photograph sent to him with Nene's head cut out of it and essentially uses written communication to dissolve the bond between he and his son. Whereas written correspondence at the start of the story was used to represent the hopeful union and integration of family, Okeke uses written correspondence to sever such connection.
The ending of the story also features the symbolic use of written correspondence. Nene has written a letter to Okeke explaining that their sons want to meet their grandfather. It is through this use of written correspondence that Okeke has recognized the error of his ways and is overcome by regret and remorse that he will lose the opporunity to see his grandsons. Written correspondence is an important symbol in the narrative. It is a symbol of both what can be and what is, as well as the human fear of what might be given our poor choices. The use of written correspondence advances the narrative through its symbolic function.