Based on the information you are having lump on the right side of my neck under your jaw line and its painful when you are eating and its difficult to swallow.
From you history and your physical weight it seem like you may be facing
2) infection of gums or
3) cold sore
Advice- consult a near by physician and have it checked. Their are chances of some infection and you may need an antibiotics to get over it.
Hope it helps
Dr. JAY PATEL