Milk Blister?

Taylor
Okay mamas...had my twins this past weeks at 34 weeks...one is in the NICU two hours away and the other is too small to latch...because of this I'm exclusively pumping...something I didn't have to do with my now two year old who latched immediately and was a feeding machine...because of the exclusive pumping I've developed a lot of blister like fluid filled pockets on my nipples....mainly on one nipple only and it's restricting the flow of milk....I can completely empty my right breast which has none of the blisters but with the left although I can feel that the breast is full....I pump and only get an ounce and it doesn't come close to emptying...any suggestions on what these blister like pockets could be and what I can do to resolve them so that I can actually pump and get all of the milk out? Thanks!