Here, we analyse the distribution of self-gravitating collapsing fluid to identify the factors accountable for the energy–density in homogeneity with the systematic construction in modified Gauss–Bonnet (GB) gravity, by taking the space–time which is spherically symmetric. The modified Einstein’s equations help us to observe the variation in the mass function due to different quantities. The dynamical equations and two differential equations for Weyl curvature are formulated and used to explore the quantities responsible for the inhomogeneity. Irregularity in the fluid is analysed by taking various cases of fluid, under the effects of f ($\mathcal{G} $) theory, where $\mathscr{G} $ is a Gauss–Bonnet term.