Although you didn't say so directly, it sounds like you may have failed to include in your bankruptcy filing a claim against someone that settled and for which you received money after your bankruptcy case was closed. If that's what happened, the trustee may have the right to that money to pay creditors. But it's impossible to say more without knowing more facts. You need to ask your bankruptcy attorney, or if you did not use one then retain one now.
You should talk to your attorney about the issue. Cases can be reopened if you did not include a pending injury claim in your bankruptcy.