Don't worry about it. In fact, feel free to take your time. I'll come around and pick you up!
Other options:
no subject
He can be wrong, sometimes (take, for example, now), so in actuality? He's a little relieved to get that text from you. ]
[ Eventually.
Hopefully soon.
Yeah.
That is also, in all likelihood, one of the few times that your boy has ever used an exclamation point in a message to you. ]