I was woken by a sharp pain on the left side of my brest bone when sleeping?

More info needed: How long did the pain last? Was it aggravated by a deep breath or chest motions? Any rib cage tenderness? Any cough or true shortness of breath? If the discomfort was very fleeting with no residual symptoms, it may have been a pinched nerve or fleeting muscle spasm. I feel that a serious problem would have continued symptoms. See your MD as needed.