Question about Miranda rights?

i was pulled over the cop asked if we had anything on us we all said no cop asked to search we again said no the got a k9 unit they found my marijuana in the car i owned up to it and when the cop asked whos it was i said its mine, the cop never read my rights doesn't he have to when questioning about that matter i thought all questions about that could be voided if i was not read my rights before questioning