It's ok.. It may screw your cycle up for the next month or so, so be prepared for breakthrough bleeding etc. You also may not get your period or get it at an unusual time since you started on the wrong day. I am guessing you are just starting the pill since you were waiting for you period? Starting on the pill can mess your cycle up anyway. Either way there's no need to panic. It will still work the same, you just may not be regular.

Okay ,thank you for your reply:)

Sometimes sex will make you bleed. It happens to me every once in a while. It shouldn't mess anything up at all, but if it happens often or if it happens with pain you may want to see a doctor.

You may have been bleeding from your period, and the pill may have stopped it. When I take my birthcontrol during my period, I usually stop bleeding.

Hotasfrick is right though, if the bleeding after sex continues or is accompanied by pain, get to a doctor!
-eff