Not a thing
Not a thing, not anything, nil, nowt, nix, damn all, sweet Fanny Adams, zip, a goose egg, nought, not a single thing, nothing at all, zero, zilch, not a dicky bird, not a sausage, sweet FA, nada, bupkis, and naught.
A trifling matter
A trifling matter, a piece of trivia, neither here nor there, a person of no importance, a person of no account, a nonentity, a non-person, small beer, a trifle, a (mere) bagatelle, no big deal, an unimportant person, a nobody, a cipher, and a lightweight.