The Oxford Thesaurus An A-Z Dictionary of Synonyms - nigglingadj.

1) irritating, worrying, worrisome, irksome, vexing, vexatious, annoying, troublesome: There are a few niggling matters that I must see my accountant about. 2) petty, nugatory, trifling, trivial, fussy, insignificant, unimportant, inconsequential, frivolous, Colloq piddling, nit-picking, US and Canadian picayune: Bill always ignores the core of a problem and occupies himself with the niggling details.