One symbol in Sophie's Choice is the classical music that the titular Sophie plays in her neighborhood.

After surviving Auschwitz, having to choose which of her two children would be put in the gas chamber, losing her son afterward, and mourning the deaths of her husband and father to the Nazis, Sophie came to America and lived in New York. She was in an abusive relationship with Nathan. Mostly their lives were bleak and hopeless; Sophie was unable to move beyond the brutality of her past. However, classical music is one positive thing that Sophie did for herself.

The music represents hope. It's a symbol of something better in a bad world. The world Sophie and Nathan inhabit might be terrible, but the music is not terrible. Played loud enough, it can be shared with everyone who is close enough to hear it. The people in the novel might be broken and flawed, but the music shows something positive within them and gives hope that no one is all bad—even if that also means that no one is all good.

I think that Sophie's number that is tattooed on her arm is a significant symbol in the novel.  It is the gateway through which all of consciousness is viewed.  The number is how Stingo first is introduced to Sophie, helping to formulate his initial impressions of her.  For Nathan, the number strikes at his own very condition of being Jewish and being driven insane partially by the "ghosts of Auschwitz."  For Sophie, the number represents her status as both victim and victimizer.  The number embodies her own struggle as a victim of the Nazis.  It also represents her own condition as the victimizer, in that the number compels her to acknowledge her own responsibility for the sacrifice of her child at Auschwitz.  She lives with the tattoo, symbolic of how she is never fully able to rid herself of the pain of her experience.  The symbolic meaning of the tattooed number is representative of how it always remains with her.  When she makes love to Stingo, the number is the only visible remain.  While she might have engaged in an "orgiastic attempt to beat back death," the tattoo, the number, is still there, waiting for Sophie, almost lingering around her no matter what.  The tattooed number becomes the ultimate symbol for Sophie as a reflection of her own pain of being in consciousness.