What dose it mean if you have a sharp pain on the side of breast?

Stitch?: Many people occasionally get a brief, knife-like stabbing pain at a point in the chest wall when they inhale. This is probably due to a transient fold in the plerua and is relieved by taking a very deep breath. There's no feeling of shortness of breath as from overexertion. If this describes your pain, then be reassured; otherwise, a physician office visit is in order.