I don't know you overall physical condition and exercising routine but the theory says you shouldn't exceed your maximum heart rate which is 226 - 61 (your age) = 165. Your upper limit should be around 75% of that maximum otherwise you are taking unnecessary risks for your health and cardiovascular system. I can not confirm if the risks are real but I have been told this at the gym. Be careful.
I think you should discuss this with your doctor. A heart rate that fast is too high and may potentially cause harm. I was told by my cardiologist that excessive exercise can sometimes 'stretch' the heart muscle (this is the phrase she used) and this can cause heart rhythm problems.
I was told to reduce the level of exercise, I was cycling 120 Mile a week and swimming about 7, also walking 5 miles a day. Like me, you may need to reconsider the amount of exercise you do.
Out of interest, do you know what your blood pressure was during that 2 hour period after exercise. You mentioned having headache also. Perhaps your blood pressure is a bit low so your heart is beating fast to compensate, it may explan the headache also.
Hi, you have recorded a heart rate above your target exercise heart rate which is not that good for your age. Firstly be sure that you recorded your heart rate by measuring pulse and not with gym equipment because that might be wrong. Secondly get your cardiovascular checkup done which may include a general chest exam, heart beat, blood pressure and an electrocardiogram. If those things are normal, everything is okay. All the best!