Sorry about that, let me know if there's any way I can make it up to you.
我很抱歉,有什么能补偿的话请告诉我,我会尽力帮忙的。
It is better to ask for help at the beginning rather than to wait until a busy period when everyone is rushed off their feet.
最好在开始工作时就请人帮忙,而不是等到大学都忙得不可开交的时候。