heat chicken breast in a pan with no oil - ok for the pan?

Doing this will not harm the pan, assuming you do not heat the pan to absurd temperatures (which is no different than if you used oil).

It may not give you ideal results for your chicken, though. Oil in the pan serves a couple of purposes. In traditional (as opposed to non-stick) pans, of course it helps prevent sticking.

It also provides a thermal coupling between the surface of the pan and the surface of the food, conducting heat from the one to the other (much akin to the way thermal paste helps your processor cooler work better).

Without this effect, you may get spottier and less reliable or uniform cooking of the chicken.

I always cook with no oil (a lot heathier than fried!). Chicken breast (sliced in 2, not to be too thick) usually cooks fast. I do the same for beef and so many other things, in non-stick pans

Yes, it will almost certainly harm the pan.

Nonstick pans are sensitive to temperature, the Teflon starts to deteriorate at about 260 C. If you have a layer of oil in the pan (really a layer, not a few droplets from a spray, that makes it worse), then the heat coming from below is pumped from the pan into the oil everywhere, and the pan is unlikely to overheat. But if you are using a dry pan, the pan is full of air, which is a pretty good insulator, and the Teflon will quickly heat up above 260 C, at least in some spots. This will shorten the lifetime of your pan noticeably.