The terminology is most commonly used in Sino-Tibetan, Japanese and Korean contexts. I suggest taking a look at this (warning: gigantic volume, probably a good idea to find an electronic version if you have access to one):
Yap, F. H., Grunow-Hårsta, K., & Wrona, J. (Eds.). (2011). Nominalization in Asian languages: Diachronic and typological perspectives (Vol. 96). John Benjamins Publishing.
But basically, a nominaliser is something that is 'more grammaticalised' than a light noun, using the usual criteria for grammaticalisation (e.g. obligatoriness, semantic bleaching, phonological reduction, boundedness, etc.). Where we draw the cut-off line between light noun and nominaliser will depend on the author, language and descriptive tradition, and if a paper uses both terms, you should look for a definition of the two (otherwise it's not a very well written paper).
By way of example, we can use Yap, Grunow-Harsta and Wrona's example of Old Chinese zhe. (Personally I have some doubts about the description, but that doesn't hurt the overall point.) In Old Chinese, they consider zhe a light noun because it can also appear in contexts where it's clearly serving as a lexical head, being modified by a demonstrative and a numeral, and modified by a relative clause introduced by zhi:
(1) 此 五 者
ci wu zhe
DEM five ZHE
'these five things'
(2) 其 謂 霣 之 者
qi wei yun zhi zhe
3 call fall ZHI ZHE
'what he describes as falling' (Lunheng)
(Note: 霣 = modern Chinese 殞)
However, 者 already different from lexical nouns (say 物 'thing') in that it is more semantically bleached - it can refer to abstract things, points in time, objects, people, etc. - it can be modified freely even without 之 (actually examples like (2) are extremely rare in my experience), and so on. So it already has a plenty of properties that set it aside from 物.
In Middle Chinese 之 started declining in frequency and examples like (1) and (2), where it displays properties of a lexical noun, were no longer productive, leaving only uses of 者 like this:
(3) 愛 人 者
love others ZHE
'those who love others'
At this point it is called a nominaliser. (In Middle Chinese, we also started seeing 者 being used to connect a clause and the lexical noun it modifies, i.e. it became a relativiser as well, though this isn't so relevant to the current question.)