If you're brewing today, I would just leave it as is and pitch it as normal. It may not start quite as fast as it would have under optimal conditions, but you'll still be pitching a bunch of nice healthy yeast, you shouldn't have any problems. And unless it's a very light, delicately flavored style I wouldn't worry about affecting your flavor/gravity by pitching the whole thing--I've pitched full starters into plenty of beers and never had any problems with the result.
That would of course be a different story if you were pitching to, for example, a very light lager, and you had a very big starter. Then you might want to think about decanting. Cheers.