The pinching sensation from wearing a bra that is does not fit correctly, or has failed structurally. They can be caused by a band that is too tight, a cup that is the incorrect size, or a part of the support structure, like an underwire, has broken or torn through the fabric and is irritating the skin. Most often felt on the "pit tits" or cleavage.
My boyfriend is going to wonder if I'm cheating on him when I take off my clothes tonight. My tits are covered in bra bites!