gerund or present participle: niggling
cause slight but persistent annoyance, discomfort, or anxiety.
"Doreen wanted to discuss matters that niggled at her mind"
Synonyme:irritate, annoy, worry, trouble, bother, provoke, exasperate, upset, gall, irk, rankle with;
criticize or annoy (someone) in a petty way."people niggling me for doing too much work"
Synonyme:complain, object, moan, fuss, nag, carp, cavil, find fault, grumble, grouse; informal
nitpick"he niggles on about the unemployed".
From a BE perspective, I don't think 'niggling' is unusual at all.