The context of this section is the Lord speaking to Oliver Cowdery, who had wondered about and already received a divine manifestation of the truth of Joseph Smith’s testimony.  In section 6 the Lord gives instructions about how peace coming to our hearts is a witness of the truth and such like.  The section ends with the verses above.

I wondered why the Lord says, “behold the wounds which pierced my side, and also the prints of the nails in my hands and feet” when the Lord didn’t appear to Oliver at that time.  What was the purpose behind those words? 

I realized that it was a reference to the story of doubting Thomas in the New Testament, who would not believe that the other apostles had seen the resurrected Lord unless Christ appeared to him.  The reference to Thomas was to show Oliver the necessity of believing Joseph’s testimony and beholding with an eye of faith the evidences that had been presented earlier in the section.

I also like that it says “look unto me in every thought; doubt not, fear not.”  It is a nice formula for choking off paralyzing doubts and fears by determinedly choosing instead to think about the Lord and what He would do.  The times that I have remembered to do this, I have been very blessed.