  The origin of simultaneous electronic, structural and magnetic transitions in
bulk rare-earth nickelates ($RE$NiO$_3$) remains puzzling with multiple
conflicting reports on the nature of these entangled phase transitions.
Heterostructure engineering of these materials offers unique opportunity to
decouple metal-insulator transition (MIT) from the magnetic transition.
However, the evolution of underlying electronic properties across these
decoupled transitions remains largely unexplored. In order to address this, we
have measured Hall effect on a series of epitaxial NdNiO$_3$ films, spanning a
variety of electronic and magnetic phases. We find that the MIT results in only
partially gapped Fermi surface, whereas full insulating phase forms below the
magnetic transition. In addition, we also find a systematic reduction of the
Hall coefficient ($R_H$) in the metallic phase of these films with epitaxial
strain and also a surprising transition to negative value at large compressive
strain. Partially gapped weakly insulating, paramagnetic phase is reminiscence
of pseudogap behavior of high $T_c$ cuprates. The precursor metallic phase,
which undergoes transition to insulating phase is a non-Fermi liquid with the
temperature exponent ($n$) of resistivity of 1, whereas the exponent increases
to 4/3 in the non-insulating samples. Such nickelate phase diagram with
sign-reversal of $R_H$, pseudo-gap phase and non Fermi liquid behavior are
intriguingly similar to high $T_c$ cuprates, giving important guideline to
engineer unconventional superconductivity in oxide heterostructure.
