Neutrinos are produced inside astrophysical sites such as the Sun, core-collapse supernovae, blazars and neutron-star mergers. Such neutrinos would change their flavors significantly owing to refractive effects of background electrons and neutrinos themselves. In core-collapse supernovae, large numbers of neutrinos are produced and emitted from the proto-neutron star after core-bounce. It is considered that collective neutrino oscillations are caused by self-interacting neutrinos near the proto-neutron star (~100 km). Such refractive effect increases energetic (anti)electron neutrinos, which is expected to affect supernova explosion and nucleosynthesis. We show a numerical result of neutrino oscillations in core-collapse supernovae and mention how collective neutrino oscillations enhance nucleosynthesis in neutrino-driven winds. Our result would be helpful to more realistic studies to reveal the origin of solar-system isotopic abundances of p-nuclei.