This is likely what you state, a sore lymph gland.
You have a chain of lymph nodes in that area. Lymph nodes are the 'garbage can of the body' and will swell in reaction to something. It could be something as simple as an irritated hair follicle in the area or a break in the skin. If it does not resolve within the next several days, or it recurrs, then I would seek evaluation.
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DrStephanie
