What do I have to do if, after completing my wajib ghusl, wudhu, and completing Fajr prayers, I later realise that I had a tiny black spot under my eye that I presume to be from my mascara?
My mascara is not waterproof.
Assalamu aleykum,
I would suggest, as precaution, to remove any traces of the mascara and re-do ghusl, wudhu and also the prayer, just to be sure that everything is performed as it should be.
It could be useful to see the rulings about the validity of wudhu’ (but also ghusl):
5. The organs of wudu must be ritually clean (tahir) before washing or wiping them.
Besides the ritual cleanliness (taharat) of the organs of wudu, they must also be exposed. In other words, there should be nothing on them which might prevent the water from reaching the skin. Special care should be taken by women in case the lipstick, nail-polish, kohl, and eye shadow are such that the water does not reach the skin. If the dirt under the long nails is not more than normal, then it will not harm the wudu.
https://www.al-islam.org/ritual-and-spiritual-purity-sayyid-muhammad-rizvi/ii-wudu
Taken from the book Ritual and Spiritual Purity by Sayyid Muhammad Rizvi, online at:
https://www.al-islam.org/ritual-and-spiritual-purity-sayyid-muhammad-rizvi
And in general, about wudhu’:
https://www.al-islam.org/articles/method-and-rulings-wudhu-shaykh-saleem-bhimji
You may also want to refer to the Risalah of the Marja’ Taqlid you follow.