Answer
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:
With regard to blood that comes out from anywhere other than the front and back passage, there is a difference of opinion among the jurists as to whether it invalidates wudu or not.
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.
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, 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.
Source: www.islamqa.info