What kind of beer was it? higher gravity, stronger beers hold up to time better than smaller beers...... If it was a Barley Wine..... good for you. If it was a hefeweizen or british bitter - probably not so much.
There is nothing left to "ferment again"...... as mentioned, taste it and see what it tastes like. If it tastes good (good enough) rack to bottling bucket with priming sugar and new (rehydrated) dry yeast. Bottle as normal. If it is bad, it is not going to get better and there really isn't anything you are going to do to make it better (IMO).
Kegged/Serving: Citra IPA, Oatmeal Amber Ale, American Wheat, Ordinary Bitter, Double IPA
Bottled: Barley Wine, Sour Belgian Golden on Cherries, Sour Cherry Stout
Primary: Heady Topper Clone, Double Citra IPA, Munich Helles
Secondary/Lagering: Schwarzbier, Oktoberfest, Bourbon Barrel Porter
Future Brews: Bo-Pilsner, Porter, APA, American Brown, Oatmeal Stout, Schwarzbier #2, British Dark Mild, More...... More....... Beer.......