Dear Sir, Sudden pain in the shoulder is normally a muscle sprain due to improper positioning and improper use, see if you can trace out to the event that led to you pain, take some rest, no need to do any type of hard work with it, and see if this settles, if your problem persist, you need to consult an orthopedic doctor.

You may be having shoulder problem or beck problem

You need further evaluation to see any reason for shoulder pain. Consult Shoulder specialist