Let me see if I can clarify the original point. Nickel is both toxic when ingested and often a contact allergen. Thus the two points are independently true of one another and in no way contradictory.
Well, certainly, nickel is toxic, like many metals. But OP's point was "toxic as hell" which seems simply wrong in any kind of context. I haven't seen evidence searching or here that nickel is more toxic than many commonly used metals and thus there seems like zero backing at all for worries about using some super strong nickel-based material. Indeed, nickel-based structural materials are used with some frequency.
Whether the material's good properties pan-out is another question, of course.
What generally happens to kids that find a US nickel on the ground/floor and swallow it without their parents notice? This must have happened a million of times.
Based on the documentation provided by a sibling comment, I think the answer is that ingestion of the metallic form is not so bad. It's some nickel compounds and inhalation that are particularly dangerous.
Not a kid, but I’m allergic to nickel and my daughter threw some quarters in my bed. I didn’t realize it and slept with a quarter burning a hole into my side. I woke up with a quarter-shaped rash that lasted about a week.
