Hollow having a slightly elevated heart rate after intense exercise is NORMAL. In facts, if your heart rate went right down to your before exercise minimum rate that would be ABNORMAL and perhaps a reason for concern.
During intense exercise, you damage the muscles a little and they need repair and also they need to replace glycogen and other stuff needs to happen so they will be good to go for tommorrow. So the body sends more blood to recovering muscles then to resting muscles and that results in a higher heart rate. It is normal for post exercise basal metabolic rate to be elevated for some hours after prolonged aerobic exercise. This is one of the benefits of exercise, the affects are longer then when you are just doing it.