As I was out running the errand I got into an accident.
What sort of accident did you get into?
A dangerous one, but I'll report it to the cops.
Everyone is human and we all make mistakes, but it's how we respond those mistakes which count. Try to make amends for what you've done and that is the first step to forgiving yourself.
I guess, I'll be watching my back since I was doing errand for a drug dealer and now the drugs are missing.
You sound like you've gotten yourself in quite a pickle. You'll have to explain to the dealer what happened; you might have to pay him off for the loss.