Is it normal for a corrected undescended testicle to feel much smaller and have the veins feel much more prominent?

Undescended testicle: It is possible that a corrected undescended testicle may not have normal growth and be smaller than the one on the opposite side. However, what you have described is consistent with the presence of a varicocele, which is identified largely by the presence of largem dilated veins. See a urologist for confirmation of the diagnosis and to see if treatment is needed.