niggle
     v 1: worry unnecessarily or excessively; "don't fuss too much
          over the grandchildren--they are quite big now" [syn: {fuss},
           {fret}]
     2: argue over petty things; "Let's not quibble over pennies"
        [syn: {quibble}, {pettifog}, {bicker}, {squabble}, {brabble}]
Source: WordNet® 2.0