Sounds like it maybe lymphedema . I had the same thing after IMRT radiation treatments and Radiologist recommended lymphedema treatments to
eliminate "turkey neck" (swelling each morning).Treatments included message therape to reduce the swelling and a neck brace to wear at night. After two years, my lyphedema is gone and occasionally returns (if my head is not elevated at night). Self massage (taught by the massage therapist) eliminate any reoccurence in a matter of minutes.