He suffered a nosebleed whilst fasting
Question

What is the ruling if a fasting person suffers a nosebleed, because this happened to me?.
Praise be to Allah.If the matter is as you describe, then your fast is valid, because your nosebleed did not happen by your choice, so the fact that it happened does not mean that you broke your fast. The evidence for that is the fact that sharee’ah seeks to avoid making things difficult for people, such as the verses in which Allah says (interpretation of the meaning): 
“Allah burdens not a person beyond his scope”
[al-Baqarah 2:286] 
“Allah does not want to place you in difficulty”
[al-Maa'idah 5:6]
And Allah is the source of strength. May Allah send blessings and peace upon our Prophet Muhammad and upon his family and companions.