  We derive the lower bound on the absolute scale of lightest neutrino mass for
normal hierarchy and inverted hierarchy pattern of light neutrinos by studying
the new physics contributions to charged lepton flavour violations in the
framework of a TeV scale left-right symmetric model. In the model, the fermion
sector comprises the usual quarks and leptons plus a fermion singlet per
generation and the scalar sector consists of isospin doublets, triplets and a
bidoublet. The framework allows large light-heavy neutrino mixing where the
light neutrino mass formula is governed by a natural type-II seesaw mechanism,
unlike the generic type-II seesaw dominance which assumes suppressed
light-heavy neutrino mixing. We demonstrate how sizeable loop-induced
contribution to light neutrino mass is kept under control such that the light
neutrino mass formula is dominantly explained by the type-II seesaw mechanism.
We examine the heavy neutrino contributions with large light-heavy neutrino
mixing to charged lepton flavour violating processes like $\mu \to e \gamma$,
$\mu \to 3 e$ and $\mu \to e$ conversion inside a nucleus. We present a
complementary study between neutrinoless double beta decay and charged lepton
flavour violation taking into account single beta decay bound, double beta
decay bound and cosmology bounds on the sum of light neutrino masses.
