Nephi clearly knows that what we know as Chapter 9 was a diversion from his planned text. Therefore, he explicitly notes that he is going to “proceed to give an account upon these plates of my proceedings, and my reign and ministry.” Note that he uses some literary parallels to tie the aside to what he will do. Nephi brings his readers back with artistry.
First, he notes that he has made a diversion and must now return. He returns to give an account “upon these plates.” It was the mention of the plates that triggered the aside. By mentioning them at this point, the diversion is less jarring. He also specifically mentions that he will record his proceedings, his reign, and his ministry.
Nephi had been required to tell part of his father’s story to introduce his own. By this time, however, he is firmly giving the account of his own proceedings. Mentioning that he speaks of his ministry reinforces the division in function that he mentioned in Chapter 9. However, he also notes that he will speak of his reign. Even though the deeds of the kings are more properly on the large plates, Nephi is creating this account as a justification for his eventual position as a ruler and teacher. Thus, some account of his reign will be required to demonstrate the fulfillment of that prophecy. We, his readers, should also note that we will hear little of his actions as king. Once he has justified that position, he will decline to give much more history.
It will be after the event of his acceptance of the kingship that he will add material that we will more clearly see as part of his ministry in the book of 2 Nephi.