Pain in chest near armpit. slightly swollen. told prob costochondritis. starting to have pain/tingling inside of arm down to pointer finger. thoughts?

Radiculopathy: 20 yo female w. "chest-armpit" pain & associated radial nerve radiculopathy describes a process occurring in region of brachial neural plexus. This could be a musculoskeletal disorder like Thoracic Outlet Syndrome or an evolving inflammatory process. The latter would best be evaluated sooner than later. See a primary care physician; urgently if there is feverishness or arm/hand weakness.