I had a mishap on aug 4, took plan b aug 5 and then i seen some spotting today which is aug 11. should i worry?

No, not yet: Spotting or irregular bleeding after Plan B is quite common and an expected side effect. It is not usually a sign or pregnancy.

Might be side effect: Emergency contraception symptoms can include spotting or bleeding, changes in menstrual flow or your period may be late or early. Take a home pregnancy test & notify your GYN if your period is 7 or > days late.