Here we see an example of the scribe writing the idea (or semantic equivalent) rather than the specific words of his copy. In the Book of Mormon, the text refers to speaking and writing both words and things, although words is considerably more frequent. Here in 1 Nephi 3:28, Oliver Cowdery, as he copied from 𝓞 to 𝓟, initially wrote things, then immediately corrected it to words (supralinearly inserted but without any change in the level of ink flow). Since either words or things is possible here, we let the earliest textual sources determine the correct reading: in this case, it is words (the reading of the original manuscript).
On two other occasions, Oliver Cowdery interchanged these same two words as he copied from 𝓞 to 𝓟:
As with 1 Nephi 3:28, Oliver immediately corrected these errors in 𝓟.
There is one example where the text has been consciously edited from things to words, although in this case Joseph Smith initially intended to change the plural things to the singular word, but the 1837 edition nonetheless ended up with the plural words:
For discussion of this more complicated change, see 2 Nephi 33:4.
Summary: In choosing between things and words, we rely on the earliest textual sources; here in 1 Nephi 3:28, we have “many hard words” rather than “many hard things”.