My sweet potatoe cassorole contains eggs I'm making it today, do I have to cook it today or can it wait until to tomorrow ?
It will hold until tomorrow if well refrigerated! ;o)
If you mean you are preparing it today to cook tomorrow, as long as it well refrigerated, it will be OK.
Incidentally, the flavor may well be improved by doing it this way. I always make my sweet potato and pumpkin pie fillings ahead of time and refrigerate at least overnight because the flavor is just better that way. (If more than a day or two, I wait to put the eggs in until closer to baking time. The sweet potato filling for the dessert I'm baking tomorrow, minus the egg, has been in my fridge since Sunday night.)
I'm not sure if this is a safety question or a quality question but my gut tells me you're better off cooking it today and then re-heating it. (That's a quality answer, not a safety answer - but you're safe either way.)