A great deal is lost in translation in this verse. It may not have the record for the number of added words, missing words, and confusing words, but it sure works hard for it. I cannot deal with everything hidden here, except in the detailed analysis, but I will highlight a few of the major elements. Of course, the basic idea of the verse, Jesus calling himself misshapen, it funny.

Many translations, including the NIV, confuse "the head of a corner," that is, a "capstone," with a "cornerstone" or a "keystone," which is in most ways its opposite idea. The capstone protects the wall; the cornerstone supports it. Instead of a square, like every other stone, the capstone is slanted to divert water from the top of the wall. The capstones in the corner were slanted in two directions. Jesus is calling himself odd, here, but his oddness serves a purpose.   The "capstone" is a play on words because "head" also means "a leader" and "corner" means a part of the community.

This verse inserts a number of definite articles, the word, "the," which is odd because, usually, the translators drop them, which we see here as well. However, there is a specific theological reason for this mistranslation, the adding of "the's." The translators what the verses to have Jesus characterize himself as more unique than his words did.  "A stone" is less special than "the stone." It is not "the head/cornerstone" but "a capstone." It is not "the corner" but "a corner." It is not that Jesus wasn't unique, we all are, but that in this regard, as a protector of others, Jesus was not unique.

The end of this verse is a direct quote from the Greek version of the Psalms 118:22 and 118:23. This means Jesus's idea was inspired by what was written.