Can You Still Fast If Your Nose Bleeds?
Question

If the blood that comes from the nose during a nosebleed enters the throat, even if it is only a small amount, does that invalidate a person’s fast?
Praise be to Allah.If the blood reaches the stomach without any deliberate action on the part of the fasting person, it does not break his fast, because Allah says (interpretation of the meaning): 
“Allah burdens not a person beyond his scope. He gets reward for that (good) which he has earned, and he is punished for that (evil) which he has earned. ‘Our Lord! Punish us not if we forget or fall into error.’” [al-Baqarah 2:286]
And it says in the hadith that Allah said, “I have done that”, i.e., I have forgiven you. 
But if it is possible to prevent it, or to spit it out, and you do not do so and you swallow it deliberately, then this breaks the fast. The evidence for that is the words of the Prophet (peace and blessings of Allah be upon him) to Laqit ibn Sabrah: “Go to extremes when rinsing your nose , unless you are fasting.” (Narrated by Abu Dawud, 2366; al-Tirmidhi, 788; al-Nasai, 87; Ibn Majah, 407. Classed as sahih by al-Albani in Sahih al-Tirmidhi, 631) 
Shaykh Ibn ‘Uthaymin said: 
“This indicates that the fasting person should not go to the extreme in rinsing his nose , and we do not know of any reason for this apart from the fact that doing so may be a cause of making water reach the stomach, which would invalidate the fast. Based on this we say: everything that reaches the stomach via the nose breaks the fast.” (Al-Sharh al-Mumti’, 6/379)
And Allah knows best.