  We have investigated the temperature driven first order metal-insulator (M-I)
transition in thin films of NdNiO$_3$ and have compared it with the bulk
behavior. The M-I transition of thin films is sensitive to epitaxial strain and
a partial relaxation of epitaxial strain creates an inhomogeneous strain field
in the films which broadens the M-I transition. Both the thin film and the bulk
samples exhibit non equilibrium features in the transition regime which are
attributed to the presence of high temperature metallic phases in their
supercooled state. The degree of supercooling in the thin films is found to be
much smaller than in the bulk which suggests that the metal insulator
transition in the thin film occurs through heterogeneous nucleation.
