Doctor Answers (10) on Muscle tear
3) muscle tear due to undue stress.
Sometimes even combination of 2 things can occour.....hence it becomes very important that you take Xray of your husbands shoulder just to be sure also a vist to orthopadecian/musculoskeletal physio is recommended.
Regards & take care.
It is not clear how you concluded it is a muscle tear. If there us any discolouration at the injured area or any structural changes like depression or unevenness compared to other side, then getting medical assistance is a wise choice. Either get an orthopaedic or physio consultation.
If nothing as mentioned as above is seen then ice and rest will help. Also look for a physio near you for rehabilitation of muscles.
If any concerns do let me know.
Wishing a quick recovery.