Sounds like aceto which, (from BeerSmith Home Brewing Blog)
"...requires both the bacterial infection to occur and also requires oxygen to grow. So in addition to having poor sanitation, you would need to have oxygen present in the beer, either by infecting the wort before fermentation has taken place or by aerating the beer during fermentation or transfer. So if you get a vinegar tasting beer, you need to check both your sanitation procedures and also be careful not to add air to your beer once fermentation has started. ...So if you have a batch of beer with an unintended sour profile, the cause is almost always ...poor sanitation when cooling the wort, fermenting it, adding ingredients to the fermenter, sampling or measuring the beer, transferring it or bottling/kegging it. Since many of these bugs are voracious consumers of a variety of sugars they can even infect your beer very late in the fermentation process and still sour your beer."
Not much can be done about it at this point. Palmer suggests cold-crashing to diminish the effect of a 'cidery' off-flavor, but it might not work in the case of aceto. Sorry, bud, but you might have to cut your losses on this one. At worst, you'll end up with a lifetime supply of vinegar.