Lead halide perovskite nanocrystals (NCs) are a class of promising light-emitting materials and have been considered as gain media in lasers. Strong exciton–exciton interactions in NCs cause an energy shift of the lowest optical transition and affect the optical gain threshold. Here, we clarify the dynamics of exciton–exciton interactions in highly photoexcited CsPbI3 NCs by double-pump transient absorption spectroscopy. This method provides control over the population of each excited state by varying the time interval between the two pump pulses. We find that the band-edge energy shift induced by the formation of asymmetric hot-biexcitons (comprising one ground-state exciton and one hot exciton) is smaller than that induced by hot excitons and hot biexcitons in the ensemble. We demonstrate that the generation of asymmetric hot-biexcitons reduces the optical gain threshold in the CsPbI3 NC ensemble.