It's funny you mention tattoos - my favourite part was the huge endorphin rush it produced. I'd wager the whole tattoo 'addiction' thing tattoo artists and the heavily inked are familiar with is usually endorphin based, with aesthetics serving as justification.

You're right about stubbing a toe or biting your tongue, but there are other activities people engage in that involve a direct seeking out of pain (Drag's in this thread talking about an unfortunate one, then there's stuff like certain activities in BDSM play [which, a surprising amount of the time, isn't always a precursor to sex], etc.). With enjoying really, really spicy stuff, there's the stimuli [pain], the endorphin release, and the justification and side effects that may bolster justification ('flavour' even in cases where little is actually detectable beyond 'mouth hot'; satiation after getting food in you, etc.).

I'm just some random guy speculating (I'm sure there's studies somewhere, though tricky to do direct research ethically), but I imagine it goes something like this for a lot of folks in a lot of contexts:

Stimuli -> Pain -> Dopamine release. If dopamine response is greater than pain response, is a good thing (then justified with reference to specific stimuli and context of stimuli). If pain response is greater than dopamine response, is a bad thing.

...reading it back I think specific type of stimuli, context, and the subject's predilections are very relevant to this calculation, but not a psychologist or neurologist, so idk.