Is it permissible to use paper tissues during prayer when there is a need for that?

It is permissible to use tissues to wipe away nasal discharge or similar impurities during prayer if the worshiper needs to do so. This action falls under the category of minor movement that does not invalidate the prayer. The criterion for determining a minor movement is common practice (al-urf): what people consider to be a small amount of movement does not harm the prayer, but what they consider to be a large amount of movement invalidates it.