I would like to start off by saying that nystatin
is an anti-fungal cream and would be effective if you would be suffering fom a yeast or fungal infection
of the vagina.
But if you do not have a yeast or fungal infection then nystatin would not be effectice at all. So, please do not self prescribe and always visit your doctor so that he/she can make the diagnosis and not you (a non medical person). Once the diagnosis is made, then if it is a fungal/yeast infection the cream will help.
Nystatin used inside the vagina should not be of any trouble, you may also use nystatin during your period although it might not be as effective as it woukd be when your period is not on. But I would only advise the use of nystatin once your diagnosis is made.
Hope this helps.