Hello. Thanks for asking from HCM. I can understand your concern. As CT scan has already ruled out brain damage, it is good for your son. Now that he has coughed up blood on next day, his oral examination is needed. It could be due to injury or erosion in mouth/gums/throat while he fell down. It usually heals. But the force of cough can again cause erosion and bleeding. Another cause is some nasal bleed in posterior part, which trickled down in throat and larynx, which came out during coughing. What you can do is, take a torch, open his mouth and check for any injury. One more point is as your son is suffering from cold, it could be due to cough with erosion due to it. You need to consult doctor in case of repeated bouts of cough with bleeding, any active bleed, you find an open wound in mouth or nose, no relief in cold. Otherwise more chances are that it will settle on its own after healing of erosion or wound. Thanks. Hope it will help you. Take care.