Malt and grain are covered with all sorts of bacteria and mold. It's foolish to think that the problem is fixed by throwing out that sack and buying another.
I'm guessing that the sack had a few drops of water fall on it and that's all it takes to enable organisms to take off and grow. I would remove those clumps and use as normal. However, I'd make sure that the malt is still crisp and flavorful. If the grains have become soggy or stale tasting, then it's ruined and out it goes.