sounds like a PVC....and most doctors will tell you that there is nothing to worry about. However I had the same thing happen about 3 days before my heart attack. SO, yes it could be nothing but then again it could be leading up to something. They may be caused by fatigue, caffeine, alcohol, nicotine or a variety of other factors. In many cases, the cause of PVCs is unknown.
Some people may feel skipped beats or galloping palpitations, and other people may not notice PVCs at all. In general, these irregular beats are harmless. However, diagnosing them and ruling out heart disease may be important. As mine were caused from a leaky valve and now have to be put on meds until eventually, I will need a replacemant valve. I hope this helps....