This question often comes up among NeoQuenya writers (most recently on Discord), how to say "I am sorry" as an expression of empathy or ask for forgiveness in NeoQuenya.
As far as I am aware we have no attested example of this phrase. It is also quite idiomatic in real-life languages - but of course also this fact allows us to establish this idiom ourselves.
There could be several candidates:
nán(ye) nairea "I am sorrowful"
nainanyes "I lament it" > "I regret it"
nán nwalmea "I am hurt/full of pain" (see also the etymology of E "sorry")
There is also apsen- which can be used in some (but not all) situations.
I personally think this is an expression that would/could use an impersonal construction, e.g.
nwalya nin "it pains me"
lue nin "it saddens me, I am sad" (this verb was impersonal when it was conceived, see lu-)