I’m not sure what the official medical advice for this is but I had to pop the blisters so milk could get out. I also tried increasing the suction but that made the blisters worse. Sterilize a needle or little sharp nail scissors and open the blisters. I thought I had a severely clogged duct and was panicking because my boobs were getting fuller and harder but no milk was coming out. I popped a blister and milk came shooting out, hit the wall across the room. Boob instantly started shrinking and getting soft
Use lansinol on nipples whilst pumping to prevent friction when pumping I also had to pop the blisters because they were clogging the milk
I'm having the same issue now at 10 weeks pp. I googled and found out what I'm experiencing sounds like milk blebs.