I understand that 'BIG' means different to different individuals. Here by 'BIG' I mean life-changing money (bigger than 20x of your monthly income).
1. Let the money sit in your bank account (wallet) for at least one month. It will allow you to settle down your heightened emotions. Just let the amount sit and do not do anything with it for at least one month.
I think this is not a good idea, because If you suddenly put an amount which is like 20x of your monthly income, the bank might be alarmed thinking this money came from something illegal. They will then conduct a review that will take a few weeks, so that would mean inconvenience to your end.
This will not gonna be the case if a person who won already has huge bank account.
If that will happen to me, I'd rather fund my own business or invest into something that doesn't bear much risks, as soon as I can to avoid unnecessary expenditures. It's inevitable not to go back in gambling once you have this amount of money.