Astronomers recognize two distinct episodes of element creation: primordial nucleosynthesis and stellar nucleosynthesis. Stellar nucleosynthesis also involves nucleosynthesis in supernovae.
Primordial nucleosynthesis is the production of certain elements from the big bang model. The primordial elements include hydrogen, helium, and a small amount of lithium. All other elements are thought to have been produced in stars (normal stellar nucleosynthesis and supernovae), though a very small amount of some isotopes can be produced by spallation reactions in the interstellar medium.
Lighter elements might have come and as suggested above Li etc from Nuclear reactions. Intermediate/Heavy elements might have come from neutron irradiation of lighter elements whereas Uranium etc might have come from supernova explosions.