update ubuntu and nova does not work

During the update of ubuntu I selected option Y, as below and broke one node, the new service starts but does not work from the cluster side, what can I do now to fix it?

Configuration file '/etc/nova/nova.conf'
 ==> Modified (by you or by a script) since installation.
 ==> Package distributor has shipped an updated version.
   What would you like to do about it ?  Your options are:
    Y or I  : install the package maintainer's version
    N or O  : keep your currently-installed version
      D     : show the differences between the versions
      Z     : start a shell to examine the situation
 The default action is to keep your current version.
*** nova.conf (Y/I/N/O/D/Z) [default=N] ?