Purity: Doubt About an Obstruction
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 289:
If a person knows that something is stuck to a part of the body on which wuḍūʾ is performed but he doubts whether or not it would prevent water from reaching that part, he must remove it or make the water go underneath it.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)