In A Complicated Kindness, Nomi notices a blood stain on her wall. She decides not to wipe it off because it reminds her that she is "at that very moment, not bleeding from [her] face. And those are powerful words of hope, really.” (89) There are many other references to blood in the novel. What is the meaning of blood here and elsewhere in the text?

It's certainly true that there are many references to blood in the novel. Nomi is fascinated by the congealed bloodstains on the wall because they remind her that she is very much alive. However, the old stains also highlight her dreary existence, one that has been purged of all vitality and purpose. 
In another passage, Nomi laments that her blood does not match Jesus's blood. We may think this comparison odd, but Nomi is said to be only five years old when she "notices" this. According to the text, Nomi once cherished a childhood book that contained many colors. One of the pages was red, demonstrating the power of the Savior's blood to save Nomi from her sins. Nomi didn't question the significance of the color until she discovered that the blood from a scratch-inflicted wound didn't match the supposed shade of Jesus's blood on the page of her favorite book. Nomi remembers poking every one of her fingers in her desperation to find the "right" shade. She also remembers how "spooked" she was to discover that Jesus's blood "was orangey in comparison" to hers.
Nomi's childhood experience and subsequent neurosis symbolize the stigma she endures as she journeys towards self-discovery and personal actualization. Because of her stringent Mennonite upbringing, she derives little pleasure from living. A rebel at heart, Nomi rejects the Mennonite code of conduct, a manifesto of provisions that includes a ban on "the media, dancing, smoking, temperate climates, movies, drinking, rock 'n' roll, having sex for fun, swimming, makeup, jewelry, playing pool, going to cities, or staying up past nine o'clock." Because of her rebellious stance, Nomi feels that her blood is "wrong." It fails to match the high standards her Mennonite faith requires of her. 
So, in the novel, Nomi's "strange" blood is a symbol of her rebellion and her yearning to explore life's purpose beyond the confines of her oppressively structured society.