probably cold air, but maybe a trip to the GP for a check up anyway, could probably do with a quick ecg/ BP check etc (though snapshots are pretty useless unless the pain is present at that time.) If it happens again, stop doing whatever you are doing, if it doesn’t pass within about a minute, or you feel sweaty/scared/short of breath/arm pain/jaw pain associated back pain and the pain isn’t alleviated or made worse by moving or taking a deep breath then its ambulance time. I know I always encourage people to go see the GP rather than call 999, but if there’s one thing the ambulance service does well its 12 lead ECG’s while the patient is still in pain, and though not prefect, or a full diagnosis, this can go a long way towards establishing wether the pain is from your heart or something else.
But, twas probably just cold air.