The massive conflict faced by Okeke in this excellent story is between the power and force of the tribe and following tradition, and between the new ways that are springing up and threatening to overwhelm the importance of the tribe and narrow lines of ethnic identity. When Okeke's son says that he will marry from outside of his tribe, he is going against tradition and his own tribe. This greatly angers his father, and Okeke as a result shuns his own son and his family. The cost of this decision is made clear in the following quote:
By a tremendous effort of will he had succeeded in pushing his son to the back of his mind. The strain had nearly killed him but he had preserved, and won.
Note the reference that is made to the "strain" of this conflict and the "tremendous effort of will" that is needed to forget his son. Okeke has to face a brutal choice: either ignore his son and cast him off because of his belief in the importance of tradition, or reject tradition and maintain his relationship with his son. His choice to embrace tradition at the expense of his son is something that has a very high price tag to it, as he discovers when he realises he has wasted his remaining years embracing tradition when he could have been embracing his grandchildren.