Swollen lymph glands can cause a lump on one side of your throat. Have you had a recent sore throat? Strep? Ear infections? Sinus infection? In some cases, even after antibiotics, some bacteria can remain, and cause a swollen gland or lymph node. A longer round of antibiotics typically clears it right up.
Have you been looked at for Costochondritis? I have had similar symptoms and am 20, that's what they say I have. But anyhow Id suggest getting your lungs and ribs imaged!