Egypt's Dar al-Iftaa answers readers' questions in various fatwas. We at See publish these fatwas. The question says:
Does blood from the nose or any wound invalidate ablution?
Answer
Blood that comes out of the nose or a wound does not invalidate ablution. However, it is preferable for one to renew ablution because of the scholars’ disagreement in this regard.
And God Almighty knows best.