The womb; the unconscious;primal yearnings/urges (especially dark waters), hence the instincts; undeveloped potentiality out of which light (consciousness) arises; creativity; the cosmic nothingness out of which creation arose.
It can symbolize a stage of ignorane/unknwoing, psychologically blind (in the dark) or hope (it’s always dark before dawn). Perhaps there is some issue to which you are not attending.

Mythologically, darkness often symbolizes the underworld or death and is related to rebirth and to Persephone and her experiences. Dark locations or areas and black spots can symbolize death. If you are in dark tunnel but can see light, it may symbolize an acutal birth memory, impending death, or simply that there is a way out of a current situation.

See tunnel, night, death.