Dreams involving injury, especially to a loved one, can evoke strong emotions and often reflect underlying concerns or fears. In your dream, your brother being stabbed might symbolize a sense of vulnerability or a fear of losing him due to dangerous behaviors, such as drug use. The act of injecting drugs, particularly fentanyl, which is known for its potency and potential for overdose, may represent anxieties about addiction or the choices he is making in his life.

The bright lights in the hospital often symbolize clarity or a need for healing. Hospitals in dreams can indicate a desire for recovery, either physically, emotionally, or relationally. Your brother's refusal to go to the hospital might reflect feelings of helplessness or frustration regarding his situation, suggesting that you may feel unable to support him or that he is resistant to help.

The presence of another person, although unclear, could signify a feeling of being watched or judged, or it may represent another aspect of your life that is connected to your brother’s situation.

Overall, this dream may be urging you to address your concerns about your brother's well-being, whether through open communication, seeking support for yourself, or encouraging him to seek help. Consider reflecting on your feelings toward your brother and how you can express your support in waking life.