I used a sterilized needle to break the white bleb on my nipple. To sterilize the needle, I Put it under fire for a while, then wait for it to cool before gently poking on the white blister. Once the blister breaks, milk flows out from the duct behind the blister. Sounds scary but it is actually not as painful as it sounds. It works for me the 4 to 5 times i had blocked duct due to white bleb on nipple. After that, do massage the hard lump behind the duct and manually express out the blocked milk.
If you have a blocked duct due to a milk blister, and you don't unblock it, pumping and latching will make it worse. Imagine a pipe filing up with water and blocked at the end. The part that is blocked will become hard and distended with all the milk in it that cannot be released.
Mothers are great! May all breastfeeding mothers enjoy breastfeeding and hope that you will have an easy breastfeeding journey!