Abstract: This study utilizes the nonlinear magnetohydrodynamic code JOREK to investigate edge-localized mode (ELM) dynamics in the EHL-2 spherical torus, which is a device specifically designed for p-¹¹B fusion. It investigates the nonlinear evolutions of multimode ELMs, as well as their impact on divertor heat loads and target erosion. Nonlinear simulations that incorporate toroidal modes ranging from n = 2 to 20 unveil a mode transition process. Although linear analysis designates n = 18 as the most unstable mode, the nonlinear interactions generate the n = 16 mode, thus becoming dominant during the crash phase. The ELM crash triggers stochastic magnetic fields, enhances cross-field transport, and causes the pedestal pressure to decrease by approximately 20%. Moreover, around 0.1 MJ of energy (10% of the total pedestal energy) is released into the scrape-off layer because of this crash. This phenomenon results in a significant heat flux that peaks at ~ 80 MW·m⁻² on the outboard divertor targets. Furthermore, the simulation result demonstrates that the physical sputtering dominates carbon erosion, with the peak erosion flux reaching 6.5×10²¹ m⁻²·s⁻¹. These findings highlight severe challenges for plasma-facing components and underscore the urgency of developing effective ELM control schemes for sustainable p-¹¹B operation in EHL-2.