Cause of left hand numbness, pain near sternal/rib joint with deep inspiration and sob. Cardiac work-up clean. What else could it be?

Hand numbness. Could be two separate issues. Hand numbness could be carpal tunnel syndrome and chest pain could be costochondritis (like arthritis). Spine problems or other problems at the junction of the chest and neck could theoretically cause both symptoms, but less likely. Your primary care physician may help our may refer to a hand/upper extremity surgeon or neurologist.
THis . This hints of beoing non -orthopeedic thus recategorized. If you have sob that persist make sure you see your pcp rather than go form one negative work up to another. While chest pain , numbness and sob could be somethinng unusaul like an apical lung lesion, you have to make sure that you are not combining your symptoms into one diagnosis. The hand numbness may be a separate issue from chest wall pain and sob.