Welcome to healthcaremagic forum.
I have read your concern.
Metallic smell in nose while breathing ,may be due to allergic rhinitis
or sinusitis .
Accumulation of purulent sputum within the nasal cavity
, which usually expectorates while coughing can also cause metallic smell.
I would suggest you to visit an ENT specialist
and get the clinical evaluation done.
Saline nasal drops can be used to prevent nasal blockade.
If there is infection within the nasal cavity,i would advice you to take ciprofloxacin
tab.as per doctor's advice.
Hope this helps.