Thanks for your question on Healthcare Magic. I can understand your concern. By your history and description, possibility of soft tissue growth is more likely. Since your chest x ray is normal, no need to worry for lung or ribs related disease. Lipoma (fat swelling) is most likely in your case. So get done ultrasound examination of local part to rule confirm then nature of swelling. If it is lipoma then surgical removal is the treatment of choice. Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks.