Bad-tempered, especially about trivial details.(adjective)
Trivial, insignificant(adjective)
Pernickety, paying too much attention to small details.(adjective)
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Use "niggly" in a sentence
"Sounds simple enough, even if you want to call it niggly on the alcohol thing."
"Have you ever sat and watched the "niggly" things which people -- especially Englishmen -- do with their hands when they don't know what to do with them otherwise?"
""niggly" heel, he was into occasional punches, but nothing major."