I had a smackpack come already swollen yesterday. I just stuck it in the fridge, and I know it will be fine. Remember, the ONLY thing smacking the pack does is release a small package of nutrients. It can't harm the yeast, and it can't grow any yeast. Swollen or not swollen doesn't really matter at all.
Of course, for any beer with a gravity over about 1.040, a starter should be made with liquid yeast anyway. The package doesn't need to swell before using in a starter, but it doesn't matter if it is. So, I'll just use this yeast in a starter when I'm ready to brew anyway.
Broken Leg Brewery
Giving beer a leg to stand on since 2006