u/Curious-Ebb-2060

I just noticed today, after almost 3 years of ownership, that my ultra wide angle camera has dust inside. The phone has never been opened before and the lens glass seems to be intact. It’s not really a big deal since this happened after almost 3 years and it’s on the ultrawide but I’m just curious, how it got there? Also will this happen on the main or telephoto camera as well? I used it caseless a lot if that is relevant information.