<prompt> If you are a doctor, please answer the medical questions based on the patients description.I noticed a large lump on my sons lower right costochondral junction yesterday. It seems to have appeared all of the sudden. There is no pain or any other symptom present. I am scared it could be some kind of tumor. He fell almost a week ago and hit his chest on a picnic table, but I dont know if it is related.  <response>: Hi. Thanks for your query. With the history of trauma a week ago and painless, symptom-less swelling in the Costco Chat Doctor. IT has appeared sudden, it is possible a small blood vessel ruptured in an already traumatized area. If the hematoma is not tight, it is painless. I do not think there is anything to worry as about. This can be confirmed by ultrasonography and or aspiration. If confirmed to be hematoma, it can be left alone, or just add an anti-inflammatory medicine for a few days. 