Costochondritis occurs in the areas where the bony ribs become cartilage and attach to the sternum, which is the long flat bone in the middle of your chest, overlying the heart. These junctions can become inflamed following blunt trauma, surgery or hard coughing. Costochondritis usually resolves spontaneously but the pain can often be relieved by taking a non-steroidal anti-inflammatory medicine such as ibuprofen or naproxen.
It is highly likely that the "itchy feeling" is a skin phenomenon and not a sign of serious internal body disease. Given that you have asthma, it is most likely to be on an allergic basis. It is not a sign of lung cancer and the likelihood of lung cancer in an asymptomatic, seemingly health 29 year old with a history of light smoking history, is infinitesimal.
I don't know if you will see this but sorry i forgot to mention that apart from the burning sensation and pain due to the costochondritis i have no other symptoms such as no cough, no wheezing etc.
Thank you