I must apologize.
申し訳ないこと
Excuse me, but...
I really don't know how to apologize to you.
I am terribly sorry but,
Pardon me for interrupting you.
I'm sorry to trouble you, but …; Excuse me, but ….
あら、申し訳ございません。
うるさくてごめん
あ、すみません。
I do not know what excuse to make.