Anxious and Obsessed with past event.

You said it was a pet puppy and 15 years ago it bit you.  If your pet puppy was safe and alive for couple of years  (as per their life span) you are absolutely fine. Remove the fear out of your mind completely. If it was something to do with rabies you would have been affected seriously within couple of days itself. The period  between dog bite infection and the first symptoms  (incubation period) is typically 1–3 months in humans. Incubation period  as short as four days and longer than three years, depending on the location and severity of the contaminated wound and the amount of virus introduced.Initial signs and symptoms of rabies are often nonspecific such as fever and headache, agitation,  fear of water,  insomnia etc. In severe cases death may occur within 2 to 10 days.

Relax and forget about that incident.