Answer
(Fatwa: 987/594/L=1432)
Actually salat al-tawaf is nafl but it is wajib due to tawaf, this salah is not wajib in itself rather it is wajib due to tawaf. However, if you performed salat al-tawaf after dawn, you fulfilled it; because nafl salah becomes valid in such times with being makrooh tahrimi.
وكره نفل …. والكراهة هنا تحريمية …… والمراد عدم الحل لا عدم الصحة كما لا يخفى وقوله وكل ما كان واجبا أى كان ملحقاً بالنفل بأن ثبت وجوبه بعارض بعد ما كان نفلا (در مختار مع شامى : 2/36)
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband