The OED gives quite a variety of dialect meanings of "nesh", of which it says the "most prevalent" is "tender, delicate, weak; unable to endure fatigue or exposure; susceptible to cold". That makes it hard to guess what it might mean in a particular context. Furthermore, the OED does not mention the only meaning in which I have ever seen the word, which is given in the glossary of Hugh Macdiarmid's collected poems as "full of awareness":

Till clear and chitterin' and nesh
Move a' the miseries of his flesh.