We investigate the effect of a polariton bath on the photoluminescence (PL) spectrum of the elementary excitations for a confined nanocavity-quantum dot (nC-QD) system. We modeled the nC-QD system as a two-level exciton in strong coupling with a single photonic cavity mode interacting with its environment. The non-hamiltonian processes induced by the environment are taken into account via a Born-Markov master equation which includes: gain and loss of excitons and photons into/out of the cavity, a dephasing mechanism produced by phonon scattering in the semiconductor lattice and gain and loss of polaritons due to the already mentioned polariton bath. In order to validate our phenomenological model, we fit an experimental spectrum to extract the values of all parameters appearing in the master equation. Our results show that polariton pumping and loss rates are comparable to the other parameters and therefore we have a first evidence that the polariton bath we proposed has a significant role in the dynamics of a nC-QD system.