Sometimes A will do that (get a quick catnap in the car and then wake up). He's pretty good about me just going ahead and putting him in his crib. He'll normally chatter away until he falls asleep again. Sometimes it's only 10 minutes, sometimes it's up to 30 minutes. So, I'd say, yes, to try again for the nap. If you're aiming for 2pm, I'd put him down with a bigger buffer so that he can try to go to sleep sooner if he wants/can...so, like, down ~1:40 or so. I'd try for the car nap if that doesn't work...because I agree, an 8 minute nap didn't do much for him after the night/day he's had.
What time do you normally get him up from his nap? Is he the kind of kid that will go to bed at his normal time, regardless of how late his nap went?