New pain - other breast - hypochondriac?

Agree with @Flaneuse - my breast surgeon says always take note of something which is painful and gets more painful. Cancer cells themselves don't have pain receptors I understand (the biopsy on my mysterious lump while still having chemo should have reassured me on that point as it hurt and the one on my cancerous lymph node did not) but cancer symptoms can certainly include pain. That said, stabby pains may be more likely to be muscular or nerve pain. 2 weeks is unlikely to be a problem (unless the pain gets much worse in which case escalate the matter). I used to get weird twinges and sensations in the 2/3 weeks leading to my annual check - that was certainly all in my head, pure anxiety. But it does get better over time. Best wishes for a reassuring result.