I lifted 25lbs for about 7 seconds & hurt my shoulder. Inner shoulder/armpit area. Stings of pain when I rotate my arm (parellel my body upward back)?

Varies. There are a number of structures in that area that you may have injured including the biceps, pec, or a part of the rotator cuff. Hopefully will resolve with rest, if not better over 3-5 days consider being seen.