Nothing happens, and if you worry then you can clean the instrument before use. That is, if you ignore my advice to tape up the crack in the box.
It's not like there are Rabies or Anthrax spores floating around in your house, and even if they were, statistically there could only perhaps land 1 or 2 on the instrument. And the minimum infectious dose of such spores is orders of magnitude greater. But even with such amounts, the shallow penetration of a dermaneedling instrument would still virtually guarantee no infection.
And that is why I have never heard of infection with these instruments (at least not with our customers), in spite of the fact that hundreds of thousands of people dermaroll. People totally have the wrong idea about the risk of infection with dermaneedling.
Only in extremely rare cases could infection occur, for example whern a person has severely reduced immunity. I think there has been only one case mentioned online. I have seen a single case only in my 7 years, mentioned online. An unverified case from an anonymous source, with no evidence offered. People are fallible and make mistakes regarding cleaning and disinfection, they keep their instruments exposed, close to their toilets etc. and there are just zero reports of infection, at least not that I know of. If it were a problem, we would read about infections more often (I never read anything about infections occurring on the big dermaneedling forums, neither on this forum, and we have approx. 30,000 dermaneedling customers).
I think that if a customer of ours would suffer an infection, they would at least email me. I have never in 7 years received a single email like that.