Maliks Muwatta Book 20, Hadith Number 97.
Section : Things that Someone in Ihram is Allowed to do.
Yahya related to me from Malik that Muhammad ibn Abdullah ibn Abi Maryam once asked Said ibn al-Musayyab about (what to do with) a nail of his that had broken while he was in ihram and Said said, “cut it off.”
Malik was asked whether some one in ihram who had an ear-complaint could use medicinal oil which was not perfumed for dropping into his ears, and he said, “I do not see any harm in that, and even if he were to put it into his mouth I still would not see any harm in it.”
Malik said that there was no harm in some one in ihram lancing an abscess that he had, or a boil, or cutting a vein, if he needed to do so.