  Recent new high-precision abundance data for Galactic halo stars suggest
important primary nitrogen production in very metal-poor massive stars. Here,
we compute a new model for the chemical evolution of the Milky Way aimed at
explaining these new abundance data. The new data can be explained by adopting:
a) the stellar yields obtained from stellar models that take into account
rotation and b) an extra production of nitrogen in the very metal-poor massive
stars. In particular, we suggest an increase of nearly a factor of 200 in 14N
for a star of 60 Msun and 40 for a star of 9Msun, for metallicities below
Z=10$^{-5}$, with respect to the yields given in the literature for Z=10$^{-5}$
and rotational velocity of 300 km/s. We show that once we adopt the above
prescriptions, our model is able to predict high N/O abundance ratios at low
metallicities and still explains the nitrogen abundances observed in thin disk
stars in the solar vicinity. The physical motivation for a larger nitrogen
production in massive stars in very metal-poor environments could be the fact
that some stellar models as well as observational data suggest that at low
metallicities stars rotate faster. If this is the case, such large nitrogen
production seen in the pristine phases of the halo formation would not
necessarily happen in Damped Lyman-alpha systems which have metallicities
always above [Fe/H]$\simeq -$2.5, and could have been pre-enriched. We also
compute the abundance gradient of N/O along the Galactic disk and show that a
negative gradient is predicted once we adopt stellar yields where rotation is
taken into account. The latter result implies that intermediate mass stars
contribute less to the primary nitrogen than previously thought.
