Sounds like inflammation, and scarring of the skin tissue from surgery, radiation and as others have mentioned, has different names. I know it as leather neck, and turkey neck. With the lymph nodes removed there is slower drainage, and gets baked up causing swelling in the face, chin, neck, and takes time to go down.

Discuss this with your doctor who may prescribe meds like ant inflammatory, physical therapy, manual lymph drainage massage, acupuncture, further testing. Light exercise, like walking while swinging arms overhead or at least above heart will help with the lymphatic drainage, also swimming, bouncing in place on a trampoline helps too, but check with the doctor for any restrictions. Good luck.