Dear Practo User,
A normal menstrual cycle can show a normal variation of +/- 7 days in a healthy female, so do not worry.
Wait for 7 days, do not take stress ( at times it causes the delay) , and since you are not sexually active , if it get more then a wk delayed , just visit a Gynaecologist , because a quick look at your profile will help evaluate the cause.
Health Tips
If you are recently gaining weight, or having pimples or facial hair growth along with irregular cycles, do visit gynaecologist.