In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
With regard to what gets onto your garment of blood or pus, if it is a small amount, there is nothing wrong with you praying in that garment. If it is a large amount, then you have to wash it or change your garment.
Answering your question, the Fatwa Center at Islam Q and A, states:
The most correct view is that it does not invalidate wudu; this is the view of Imam Malik and Imam Ash-Shafi`i (may Allah have mercy on them both) and it is the view favored by Imam Ibn Taymiyah.
If it is a large amount, then you have to wash it or change your garment, according to the majority of jurist.
Some scholars are of the view that blood that comes out of a person’s body from anywhere other than the front and back passages is pure.
Sheikh Ibn Uthaymeen (may Allah have mercy on him) said: The view of those who say that human blood is pure is a very strong view, because the texts and analogy indicate that. (Ash-Sharh al-Mumti, 1:443)
Almighty Allah knows best.