This is bit hard to gauge without knowing more about the story. In English-speaking countries, saying 'apology accepted' is a normal way to respond to an apology. It's not impolite and he has tried to put you at ease at the same time by telling you not to worry. From his response he considers the situation over. You made a mistake, you acknowledged the mistake and apologised, which he has accepted. What he said indicates he is not going to hold the mistake against you and you can both move on. I'm not really sure what you mean by 'not humble.' Unless you feel that he also made a mistake which contributed to your error, which he has not apologised for. Maybe there is a greater subtext here and you have reasons why you do not trust him and have a bad feeling about his response. And perhaps in your country the cultural etiquette surrounding apologies is different, I do not know. Like I said it's hard to gauge without knowing more about the specific circumstances.