According to Andrew Skinner, the Lord explicitly stated: "thou art Nephi, and I am God" (Helaman 10:6). Since it is reasonable to assume that Nephi knew who he was, and since we know that the Lord speaks no words in idleness, such a statement must have profound meaning. It appears to be an acknowledgement, in the presence of divine witnesses (the text says "angels"), of a special relationship of mutual love and respect between the Lord and Nephi. The Lord was claiming him as his servant and part of his spiritual posterity. It was also formal acknowledgement of a special covenant which the Lord was confirming with Nephi.
The Lord's statements as recorded in this section of the book of Helaman fit perfectly the pattern of formal covenant making in the Old Testament world. The main features or components of covenants (and even treaties) established during Mosaic times include formal mention of the parties involved in the agreement; the stipulations of the covenant; the witnesses to the covenant; the statements of blessings and cursings; and the oaths confirming the promises made (see Interpreter's Dictionary of the Bible 1:719-720). [Andrew C. Skinner, "Nephi's Ultimate Encounter with Deity," in The Book of Mormon: Helaman though 3 Nephi 8, According to Thy Word, p. 123]