Is it permissible for a pilgrim in a state of Ihram to use a sewn towel for drying, and how does he dry his head without covering it?

There is no harm in a pilgrim in the state of ihram using a towel to dry his limbs, because he was only prohibited from wearing tailored clothes that fit the limb. And using a towel is not considered wearing tailored clothes. If the pilgrim in the state of ihram fears harm and needs to dry his head with it, it is permissible, and he must offer a fidyah (expiatory sacrifice).