skipped appointment for contraceptive

I would wait 2 weeks and take a hpt first, juuuuuust in case

hi all,

i had my very first contraceptive-injection on the 02/06/12 (first one after using triphasil for the past 2yrs)
I was due last mon (23/07)did not go nd had sex .
will there be anything wrong to just go for the injection or must i check first .