Why is the main character, Nnaemeka, unsure of whether or not his father will be happy about the engagement?

In Chinua Achebe's short story, Marriage is A Private Affair, the lead character, Nnaemeka wants to marry Nene, the girl that he loves, but his father wants him to marry to the girl that he has chosen for his son. It is the beginning of the conflict between the father and son and also between the traditional and modern values which runs throughout the story. Therefore, Nnaemeka is unsure what will his father say, how will he react after learning that he is going to marry the girl that he himself has chosen.