I have just discovered the source of this horrible pain I've been experience while breastfeeding my 1 year old. It seems to be an underground blister on the nipple kind of like a pimple I guess. It appears white when squeezed and is really painful! Of course it's on the side that my son prefers too. Any idea on what it is and how to get rid of it???? He won't take bottles or formula either so really dreading feeding times.