Thanks for your question. Any new lump or bump that persists for any amount of time should be discussed with a doctor
to make sure that it is not something serious. There are many bones in your ribs and thorax that all have various joints. Just like any joint, these can become inflamed and tender, and when they do so there can be some swelling as well. There are also many lymph nodes that are involved in fighting infection and help your immune system. When you have an infection, the blood and immune cells rush to the local lymph nodes and cause them to enlarge as they fight the infection. More rare but much more concerning are the different kinds of tumors that can be affected with malignancy. There are some that are specific to the immune system and the blood system as well, and there are others that have more to do with the chest and the breasts (yes, even guys can get breast cancer although it is rare). Please speak with your doctor to determine if there is more that needs to be done to make sure that this bump is not something more serious, and do this soon.