I Feel A Slight Pulsing Sensation In My Sternum But

I feel a slight pulsing sensation in my sternum but absolutely no pain. While I am exercising or moving I feel nothing and actually exercise at least 5 times a week . I am 61 years old. Just seemed to start after I had a bad cold. It has lessened with time but is still there and feel it when I an resting. Sometimes don't feel it at all. Doctor put me on prenaozone for my cold symptoms but since have finished that.