Combining in situ high-pressure X-ray scattering with transmission electron microscopy, we investigated the pressure-induced structural switches between the rock salt and amorphous phases as well as the associated mechanisms of their crystallization and growth in 6 nm PbTe nanocrystal. It was observed that rock salt PbTe nanocrystal started to become amorphous above 10 GPa and then underwent a low-to-high density amorphous phase transformation at pressures over 15 GPa. The low-density amorphous phase exhibited a structural memory of the rock salt phase, as manifested by a backward transformation to the rock salt phase via single nucleation inside each nanoparticle upon the release of pressure. In contrast, the high-density amorphous phase remained stable and could be preserved at ambient conditions. In addition, electron beam-induced heating could drive a recrystallization of the rock salt phase on the recovered amorphous nanoparticles. These studies provide significant insights into structural mechanisms for pressure-induced switching between amorphous and crystalline phases as well as their associated growth processes.