بسم الله الرحمن الرحيم
If blood or pus smears the body and dries then it should be cleaned during wudhu and ghusl because both these things are impure and they could be removed by rubbing gently.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.