Al-Hasan ibn Mahbub narrated from Abu Ayyub, from Muhammad ibn Muslim, who said:
I asked Abu Ja’far عليه السلام about a person in a state of janaba (ritual impurity) who has sores. Imam عليه السلام said: "There is no harm if he does not perform ghusl; he should perform tayammum."
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 1, p. 194