Purity: Obstructions on Wudu or Tayammum Parts
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 337:
If something is stuck on a part of one’s body on which wuḍūʾ or ghusl is performed and it is not possible to remove it, or the difficulty involved in removing it is such that it cannot be endured, then the person’s responsibility is to perform tayammum. However, if the thing that is stuck is on a part of the body on which tayammum is performed, it is necessary to perform both wuḍūʾ and tayammum. Furthermore, if the thing that is stuck is some form of treatment, it is ruled to be jabīrah.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)