All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is not permissible for a Muslim to disclose his 'Awrah (parts of the body that must be covered in Islam) during the prayer even if he is praying in a dark room. If one performed the prayer while unveiling his/her 'Awrah, he/she should make up this prayer.
Allaah Knows best.