Reference: Fataawa Ramadhaan – Volume 2, Page 476, Fatwa No. 416
Question: With respect to blood flowing out, what are the situations in which it nullifies the fast?
Response: The fast is not nullified except by cupping according to that which is correct. There is a strong difference of opinion in this and many see that the fast is not nullified even by cupping. However, the consensus is that cupping nullifies the fast.