Without being able to see him, it is hard to tell. How long have they been present? Is the child in any pain or not eating? It is possible that he could have some sort of bone structure problem or it could be something like neuroblastoma. You will need to take him to the doctor.

The xiphoid process, which is the tip of the sternum (breast bone), is very flexible in newborns and sometimes stick straight up creating a hard little bump right in the midline of the belly just below the rib margin. It's perfectly normal but it really frightens parents when they feel it.

I suggest calling your pediatrician for assurance.