Similar word to pesterer:

besetment, blister, bore, bother, botheration, botherment, bum, creep, drag, drip, exasperation, frump, gadfly, headache, inconvenience, infliction, insect, irritant, irritation, louse, nag, nudge, offense, pain, pain in the neck, pest, pester, pesterer, pill, plague, poor excuse, problem, terror, trouble, vexation