I had the lump under my chin after rads, and then after the neck diseection. It's an accumulation of lymphatic fluid drainage due to the damage or removal of the nodes in the neck, and will probably subside, but let the doctor check it. I called it my turkey neck. Some have manual lymph drainage massage by a therapist trained in this, which name escapes my mind..chemo fog. The massage has to be done in a certain way, direction, pressure, and depends on the area of the face and neck, so just massaging it may not be helpful.

A radical neck dissection, as you probably know, invloves the removal of the neck muscle, vein, and nerve, in addidtion to lymph nodes in level II-V, and some do have neck, and shoulder weakness, pain and probably the baby weight is added stress. I'm gong to PT again to help mine, and doing stretching exercises, which I'm sore for a few days after, but seems to help.

The hair loss on the nape of the neck, hairline, is from radiation too, which continues to work 6 weeks post treatment. I didn't have Carboplatin, but it's close relative, Cisplatin, which also causes hair loss to some extent.

I hope this helps.