Unfortunately, you need to get it out. Otherwise, you can end up with an air pocket, or just a plain old hot spot where coolant isn't flowing past an area. Uneven heat equals uneven expansion, equals improper fittment, equals uneven and premature wear. It may involve another hour or two of swearing, but you'll need to pull it out. Finding ways to bend it are your best bet. Once is starts to take the shape of a taco, you'll be able to pull it right out. Sometimes frustrating, but always worth it to know that the job is done right.
