godan verb (-ru), intransitive verb
be greatly obliged; be very sorry
Formal, somewhat old-fashioned expression of deep gratitude or apology. Often used in set phrases like 痛み入ります.
お心遣い、痛み入ります。
I am deeply grateful for your consideration.
ご迷惑をおかけして痛み入ります。
I am very sorry for causing you trouble.