Purity: Wudu with a Covered Wound on the Face or Arms

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 327:

If a wound, boil, or broken bone that is covered is on the face or arms, in the event that it is harmful to uncover and pour water over it, one must wash as much of the area around it as possible. And based on obligatory precaution, one must also wipe over the jabīrah.

-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)