You can always bring your own case as long as you were not a party to the settlement. Though for it to be successful you’re probably going to have to show you suffered more than the average class member.

For instance you buy a dishwasher that is faulty. There’s a class action settlement, but for you, the dishwasher ruined your apartment and the neighbors downstairs. You can opt out and sue directly even if there’s been a class settlement.