All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
First of all, it is not permissible for you to open an account in a Bank that deals with Riba (interest and/or usury); for more benefit on the ruling on dealing with such a bank, please refer to Fatwa 90054.
Secondly, some scholars are of the view that you should withdraw the money and spend it in charitable fields, like sponsoring the orphans, helping the poor and needy and the like. But first and foremost, you should repent to Allah from what you did because Riba is a major sin. Spending the money in charitable fields as we mentioned –even if this is required –is not enough as repentance.
Thirdly, the ruling of the prize is the same as the ruling of interest; you may leave it for them and you may take it and spend it in charity or spend its value in charity, but you should not use it for personal benefits as you received it in a forbidden manner so it is an ill-gotten earning.
Allah knows best.