Pain after CABG. Also little worried.

Hi Sir/Mam, My dad is 64 years old, has undergone heart bypass surgery (CABG) 3 months back . He is regularly doing yoga, exercises and walks as suggested by doctor and physiotheraphist. Till now he never experienced severe pain even when he was just discharged from hospital. He is following the same diet, exercises. A month back he is done with his first review with surgeon as well after 6 weeks from the date of discharge. Doctor said that report says everything is normal he has to continue with same diet and exercises thats it. That time also he had not experienced any pains. But from last 2-3 days he is experiencing severe pain in neck, upper chest part(just above the surgical area), left arm, elbow, fingers. He couldn't even sleep last night. When he was trying to sleep straight, left/right side he was feeling so much of pain which was not allowing him to sleep. He felt in a such a way that below part of left arm was pulled by someone inside. Pls suggest, Dad also little worried.