> It is administered with a disposable needle-free injector, which uses a narrow stream of the fluid to penetrate the skin and deliver the jab to the proper tissue.

I've never heard of something like this [0],[1]. It's not injector-free, but rather needle-free.

[0]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4675000/

[1]: https://theconversation.com/a-covid-19-vaccine-may-come-with...

They've existed for quite a while now - https://en.wikipedia.org/wiki/Jet_injector#History

That does not sound pleasant, though it seems they're less painful than needles from a bit of searching around.

Last jab I got I was sitting and waiting and I was looking around distracted and suddenly I felt the nurse was pushing the cotton already. She had injected me and I didn't feel anything at all. How are needles painful?

It varies on person (including mental state), needle size, and nurse/operator skill. I suspect one bad experience with a needle can prime someone for a poor response in follow up experiences.

Indeed. Both covid jabs were perfectly fine, it probably doesn't get any more painless than that come to think of it, but I had a regular one in February with a cocktail of various vaccines and that one was much less pleasant.