Don't throw it away yet! If you bound off the neck, you can take out the bind off, take out a few rows and bind it off loosely again.
If it's a top down, I imagine you can still take out the cast on, though it's harder, take out a few rows and bind off those stitches.
In the future, you can probably still follow the pattern but use larger needles on the neck parts and bind off very loosely--with an even larger needle. I've found that it's usually the bind off that makes it hard to put over a 'brainy' head.