Praise be to Allah.
There is nothing wrong with that, unless there is any najaasah (impurity) or dirt on it, in which case it should not be used as a sutrah because the Prophet (peace and blessings of Allaah be upon him) forbade spitting in front of oneself. But if there is no visible dirt or najaasah on it, then there is nothing wrong with using it as a sutrah. End quote.
Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him).