Can punching my iPhone damage it? Sometimes, when I'm suddenly frustrated by something problematic I read on Reddit, I punch my iPhone SE (the 2016 version) screen from a couple inches away using my finger joints while holding it in my other hand (I know, bad habit). I'm wondering whether this bad habit has any risk of causing long-term negative effects to my iPhone, like breaking something on the PCB or damaging the battery.
Sure it can, just like dropping it on the floor.
999 times you'll get away with it, the 1000th you'll break something.
As this is entirely behavioural rather than accidental, I'd suggest you learn to not do it.