Pokemon can't evolve in the Daycare nor do the gain happiness or EV's. All you have to do is. Level it up outside the daycare. If this doesn't work A. Take the Everstone off, B. Stop pressing 'B,' C. Consult someone of a higher level of knowledge, or D. Level it up again.
If this doesn't work get a new Nidoran, is it that much of a problem? It may just be a glitch.
Hope I helped!~-~SwagMeowth