Blister on nipple incision after breast lift, 6 weeks post op (Photo)

I've had 3 blisters so far. I've only including 2 in the photo. The second one is the most recent blister that appeared today. I've noticed that with the other ones, once it's pops, liquid comes out (its odorless), and a tiny hole forms. Why does this happen? And how do I prevent this from happening again? How do I go about this with my new blisters? I still wear my post op bra, and don't sleep on my belly