Praise be to Allah.
If a person is wounded in one of the areas of wudu’ and is not
able to cover the wound with a bandage, he should perform wudu’ except for the
wounded body part, for which he should then perform ablution with sand (tayammum).1
(Note that this means one performs normal tayammum, not actually placing the
sand on the wound itself.)
1 Al-Mughni ma’a al-Sharh il-Kabeer