Sharp Stabbing Pain Under Shoulder 2 Weeks Post-op Breast Augmentation

Any sharp pain of that level should be evaluated by your surgeon. However, in my experience the shoulder blade pain can be due to improper posture compensating for the pectoralis pain. Actual pain inthe armpit may be due to pressure on the nerves exiting the chest and entering into the arm. In either case seek evaluation by your surgeon for reassurance. IT could be due to other causes. The exercise video below may help but only after meeting with and approved by your surgeon

The pain you describe is unusual for an augmentation mastopexy. Shoulder pain is often referred from another area and may be entirely unrelated to your surgery. In some cases, a pneumothorax (air around the lung) may cause this type of pain. Either way, I recommend you see your surgeon for an examination. 

This is truly unusual.If the pain increases on deep inspiration you wonder if their is some pleurisy or a sensory nerve that is being irritated.Assuming their is no infection or fever you may want to try a medrol dose pack which is a steroid and can reduce inflammation.