Is the ghusl valid if, after performing ghusl and prayer, I remembered that a corrector was on my finger and I did not remove it before ghusl, knowing that I intended to remove it but forgot?

If the suspended substance has a mass that prevents water from reaching [the skin], then your ablution is invalid, and you must remove it, wash what is beneath it, and repeat the prayers you have performed. It is sufficient to wash only the affected area. However, if the residue is merely a color that does not prevent water from reaching [the skin], then your ablution and prayers are valid.