cause the body to produce an excess of histamines. This is the cause of the "itches" which is a common occurrence in all opiate
Ones nose itching could be a symptom of this, however there is also another theory to consider.
If the opiate in question was snorted it could just be irritation from snorting
the compound in question. There may be other things cut into the compound which cause an irritation also.
The most likely explanation would be the excess of histamine production which is common of almost all opiate / opioid compounds though.
Hope this has been of help