Cut the tip of my pointer finger off 8weeks ago. how long does it take to heal? how long will it be sensitive.

Depends: The time for healing depends on the size of the defect, how much skin was lost. It will be sensitive for quite a while, often for months, but should eventuall be fullly useful.

Maximize healing: The real question is what not to do that slows down healing. Avoid using alcohol, peroxide, hibiclens, betadine, and bleach solutions. Inflammation ( red, hot, swollen, tender) is important to healing so anti-inflammatories (motrin, advil) are bad. Cover the area with a clean dressing changed every other day and protected from trauma. Antibiotics do not help healing unless it is truly infected.