Hello and welcome to Healthcare Magic. Thanks for your query.
I understand your concer about your nephew. The symptoms you are describing could have resulted from 'snorting' the cocaine. Another possibility is that these symptoms could be indicative of an allergic rhinitis
Since, you say that the symptoms are quite severe, it is advisable to see a doctor as early as possible. He will need a phsysical examination, including an ENT examination to ascertain the cause of his symptoms. Further treatment will depend on the likely cause.
Wish you all the best.
Dr. Jonas Sundarakumar