I laid with my head in gasoline that dripped under a vehicle for a few minutes until i felt my head is wet, and then immediately washed it off with cold water, should i seek medical attention, or is the sort period of exposure not a concern?

Depends: The gasoline does not penetrate your normal skin & such skin exposure is not a problem for most. If you inhaled enough fumes that you start having a deep cough/difficulty breathing such exposures occasionally cause lung issues. (Even chemical pneumonia) . If you have a minor cough that does not get bad over the next 6 hrs I would expect no problems at all.