Your heart rate is within normal limits and rises appropriately with exercise. Unless you develop new symptoms such as lightheadedness, worsening shortness of breath, chest pressure, I would not worry about it. Mention it to your doctor and maybe have an ECG to make sure it is a normal rhythm. Hope this helps!
I'm pretty sure anything between 60-100 is perfectly normal. My cardiologist would even go as far as saying anything between 45-110 is normal if you're not experiencing symptoms. If your heart is structurally sound (have you had an echo?), and if your heart rate raises appropriately with activity, I don't think you have a problem.
Mine resting can go below 50, no lower than 45 though. normal for me is 55-62 unless I am doing exercise of some sort. Has been that low since I started seeing Drs. 40 years ago, I am 72 and still have this low H/R.