We have studied high density effects and their spatial distribution on the absorption spectra of excitons localized at a specific planar-defect structure in layered BiI3 crystals in which a quasi two-dimensional space with the translational symmetry is realized and the center-of-mass motion of excitons is confined. The exciton transition energy was examined by a space-resolved pump-probe method. The blue-shift of the transition energy has been detected not only at the exciting laser spot but also at the different site away from the exciting point. This is the first observation of high density effects on the exciton spectra at the isolated area from the source due to the spatial propagation of excitons.