I have them on mine, too. You have to get down low and look at them in just the right light to see them easily. It's not from wood - there is none in the hull - but from impurities in the lay-up of the polyester. It only happens to boats which are left in the water; more likely in warm, fresh water from what I've been told.
My boat was heavily discounted because of the blistering and I bought the materials to repair them after getting the boat. Then I just never got 'round to fixing them; it sails just fine. Only racers would notice the hit in speed. If you don't leave your boat in the water, the problem won't get worse. But if you're a stickler for having everything perfect, it might drive you crazy just knowing they're there and it would be worthwhile to get them repaired.