In this verse we have a sequence of six logically connected and parallel if-clauses, where each one is connected to the previous clause by the same coordinating conjunction, and. Unfortunately, the 1830 typesetter accidentally dropped the second of these and ’s, thus disturbing the systematic cadence and parallelism of the original text. The 1874 RLDS edition restored the and, but without access to the printer’s manuscript.
Summary: Restore the missing and in 2 Nephi 2:13 (“and if ye shall say there is no sin”).