Watch out, bro! That could be an allergic reaction, and/or you're pinning too close to an artery or major vessel. A metallic taste and coughing, are two key symptoms of anaphylaxis (potentially fatal shock). I'd find out why that's happening, and do something to prevent it (change brands, change pin sites, etc).
What exactly causes the smell we experience when punched in the nose? I really don't know. But, I experience the same smell (but much milder) when on some cycles.