The photoluminescence of a GaAsN alloy with 0.1% nitrogen has been studied under pressures up to $8.5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ at 33, 70, and $130\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. At ambient pressure, emissions from both the GaAsN alloy conduction band edge and discrete nitrogen-related bound states are observed. Under applied pressure, these two types of emissions shift with rather different pressure coefficients: about $40\phantom{\rule{0.3em}{0ex}}\mathrm{meV}∕\mathrm{GPa}$ for the nitrogen-related features, and about $80\phantom{\rule{0.3em}{0ex}}\mathrm{meV}∕\mathrm{GPa}$ for the alloy band-edge emission. Beyond $1\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, these discrete nitrogen-related peaks broaden and evolve into a broad band. Three new photoluminescence bands emerge on the high-energy side of the broad band, when the pressure is above 2.5, 4.5, and $5.25\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, respectively, at $33\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. In view of their relative energy positions and pressure behavior, we have attributed these new emissions to the nitrogen-pair states $\mathrm{N}{\mathrm{N}}_{3}$ and $\mathrm{N}{\mathrm{N}}_{4}$, and the isolated nitrogen state ${\mathrm{N}}_{x}$. In addition, we have attributed the high-energy component of the broad band formed above $1\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ to resonant or near-resonant $\mathrm{N}{\mathrm{N}}_{1}$ and $\mathrm{N}{\mathrm{N}}_{2}$, and its main body to deeper cluster centers involving more than two nitrogen atoms. This study reveals the persistence of all the paired and isolated nitrogen-related impurity states, previously observed only in the dilute doping limit, into a rather high doping level. Additionally, we find that the responses of different N-related states to varying N-doping levels differ significantly and in a nontrivial manner.