niggle

from The American Heritage® Dictionary of the English Language, 5th Edition.

• intransitive verb To cause one to be persistently preoccupied, annoyed, or uncomfortable.
• intransitive verb To pester someone or be annoying or uncomfortable in a persistent way.
• intransitive verb To be overly concerned or argumentative, especially about something petty; fuss.
• intransitive verb To preoccupy, annoy, make uncomfortable in a persistent way.
• intransitive verb To pester or nag (someone).

from The Century Dictionary.

• To eat sparingly; nibble.
• To act in a mincing manner; work in a finicking, fussy way.
• To trifle; be employed in trifling or petty carping.
• To fret; complain of trifles.
• . To draw out unwillingly; squeeze out or hand out slyly.
• To play with contemptuously; make sport or game of; mock; deceive.
• To fill with excess of details; over-elaborate.
• noun Small cramped handwriting; a scribble; a scrawl.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb obsolete To trifle with; to deceive; to mock.
• intransitive verb To trifle or play.
• intransitive verb Prov. Eng. To act or walk mincingly.
• intransitive verb Prov. Eng. To fret and snarl about trifles.
• intransitive verb To move about restlessly or without result; to fidget.
• intransitive verb To be finicky or excessively critical; to potter; esp., to work with excessive care for trifling details, as in painting.
• transitive verb To use, spend, or do in a petty or trifling manner.
• transitive verb To elaborate excessively, as in art.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A minor complaint or problem.
• noun obsolete Small, cramped handwriting.
• verb To trifle with; to deceive; to mock.
• verb To dwell too much on minor points.
• verb To fidget, fiddle, be restless.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb argue over petty things
• verb worry unnecessarily or excessively