You should make a starter for this yeast before pitch. Having said that as long as your smack pack is viable at this point , if your wort is cooled etc I would pitch and move on. You may have a big lag time.
I have done the same thing ( I always make starters for smak packs now ). In some cases I have pitched a smak pac and had visible fermentation start in 5 hours.
Well, it's too late for a starter now. Typically you do one 1-2 days prior to your brewday. There's some good threads here, just search for 'starters.'
You'll be fine, don't sweat it. I've been using smack packs for months w/o a starter and my beers turned out great. It's when you get into the higher OGs and bigger beers that you really should use a starter.
Its a Boston Ale so I dont think it should have a really high OG This is my first time using a smack pack, last time I just used whatever yeast came with my kit, but this time I used a recipe instead of a kit, im kinda excited