Niggle is an onomatopoetic word—one of several in the English language that sound like their meaning. According to the Oxford English Dictionary, the original British meaning of niggle referred to small, cramped handwriting. I suppose trying to read such writing could be niggling.
Niggling is a persistent annoyance, something eating away at you bit by bit. Merriam-Webster describes niggle as spending too much time and effort on minor details. Some of us find people who major in minors irritating. Niggling persons wear our patience thin.
Nitpick is a good visual synonym. I imagine someone picking at the ubiquitous lint that affixes itself from a white napkin to your black slacks after a meal at a fine restaurant. A nitpicker won’t quit until she has removed every last vestige of that napkin. Or picking at a scab until it bleeds. A niggler is persistent.
Nagging is closely related to niggling, but is more negative. A nagger is an unyielding fault-finder, a constant criticizer. You might be able to ignore a niggler, but a nagger might really get under your skin.
Now there are apps to handle at least some of life’s annoyances and distractions. Niggle It is a mobile app that reminds you when warranties, agreements, memberships and the like are about to expire. No more need to track such niggling details in your gray matter. Let your mobile device handle it. For those pesky irritants or pet peeves that keep you from enjoying life, there’s a life coach app—Niggle Lite. Simply key in what’s bothering you and the app offers up quotes and questions that help you see your problem in a different light. I don’t use those apps. I would have a niggling feeling about losing my phone..