As the question implies, I'm interested in only the semantical aspects of the two words I've listed. I've looked up these two words on some online dictionaries. After some searching, I've noticed that the third definition of nexus and the first/second definition of locus are nearly identical in meaning.
Cambridge Dictionary lists the definition of nexus as "an important connection between the parts of a system or a group of things" Whereas locus is defined by the same online dictionary as "the place where something happens or the central area of interest in something being discussed:" Here are some examples to expound my point:
Example 1: For us, the island had become the locus of the struggle.
Times Square is the nexus of the New York subway.
Example 2: The real nexus of the money culture was Wall Street.
The community is a locus of healing, not the hospital or the clinic.
In the two previous examples, my brain's understanding of these two words has led me to perceive them as sharing the definition of "a place or locality as the cause or source of great activity".