It's not ruined, it's just taking longer for the yeast to replicate to the level needed to ferment the brew. They're going to be more stressed and their cell walls won't be as strong, but they'll get the job done. Just be prepared to give the batch more time to get rid of any off flavors, or to become better/great.
If you cannot get a larger flask, look into making stepped starters (yeastcalc.com makes it easy to figure out). If you're not already doing so, start using yeast nutrient in the beer wort boil to help the yeast out too. I'd also go ahead and get a pure O2 infusion setup ASAP. I've listed the parts I don't know how many times on various threads already. 60-120 seconds of pure O2 at 1-2LpM can do wonders for your beer.