This study talks about nerves of the penis in some detail: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7354288/
It specifies for example how, while the dorsal nerve of the penis innervates the glans and the upperside and sides of the penis, the underside or ventral area (sometimes called corpus spongiosum) is mostly innervated by perineal nerves.
It also refers to this study that says the latter nerves are partitioned into nNOS positive and negative parts:
So I wonder if the underside of the penis is mostly affected by numbness for me (or maybe someone else), if it might simply have something to do with nNOS. However these are only some of the most shallow observations, I don’t know if nNOS is actually involved sensation/feeling or just the usual erection stuff.