Dorsal nerve.
AJE,
Did you know this site has a search feature that allows you to look for topics in old posts? The button at the top of each page labeled “search” will get you there. I just did a search for “nerve anatomy” and came up with this thread that has some links on the subject.
The dorsal nerve location is probably as different from man to man as is the location of the big dorsal vein. Generally the nerve is somewhere on the top (or dorsum) of the penis. I think most damage to the nerve can come from prolonged compression while hanging weights and manual tugging or jelqing probably isn’t as dangerous as you might think. (More experienced PEers may have differing opinions from this admitted PE newbie.)