What happens when a divorce is nullified,but I'm already remarried?

Why was the divorce nullified? You need to get the divorce finalized right away. If you are remarried, move out temporarily.

You need to give information.

Unless you are living in a country where you can be married more than once. If a divorce is nullified, then you are still married to the first person and the marriage to the 2nd person is not valid.

Before you remiarry you have to wait till the first divorce is final. That varies by location.

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Before you remiarry you have to wait till the first divorce is final. ...

Which suggests that OP has used the wrong term, "nullified". Absent very unusual circumstances which I cannot even guess, a final decree of divorce, unless appealed, would not be nullifiable. One of the parties could, perhaps, appeal a final decree. That generally must be done within a month or so. But even a successful appeal would very seldom, if ever, result in the decree being nullified.

Unless, of course, the divorce was in some exotic, non- U.S. non-Commonealth country.