The narrator of The Scarlet Ibis reflects that within me there is a knot of cruelty borne by the stream of love what does he mean by this?

The narrator is expressing the complex combination of love and regret he feels towards his younger brother. He recognizes the contradiction between his genuine care for the boy and the moments of cruelty or harshness that have occurred within their relationship. This inner conflict is represented by the metaphorical "knot of cruelty" within him that is intertwined with his love for his brother.