Right armpit been sore for few days, and swollen, dont feel any lumps. is this worrisome? had breast exam today dr said he felt nothing abnormal.

Strain? : It is good that Dr did an exam & thought normal- likely this means no swollen lymph nodes or abscesses /infections. Tenderness could be related to a muscle strain or perhaps something deeper down. You could try warm compressed & ibuprofen but if not improving in a week or so I recommend recheck by Dr & possibly further testing.

Armpit sore : Why is your armpit sore? Skin problem: infection, rash. Muscle strain? Inflamed lymph node( even while feeling no lumps). Nerve pain (rare) Intercostobrachial neuralgia. There are several possibilities