Dash warning lights on after flushing out inadvertent petrol in a diesel avemsis

[Christena]

My husband put petrol by accident into my avensis2016 diesel saloon.He quickly realised his error and the RAC sorted it out and he was back on the road running normally.The electronic brake system warning lights are both on and also there is a permanent message on the dash board to attend to it.The engine system sign and another symbol sign are also on. The brake only works if I manually pull it. Any ideas on what has happened. The tax guy took two hours to flush out the petrol and had the back seat out at one point. Can I reset the warning lights by temporaryially disconnecting the Battery??