Im havaing black spots on upoer molar teeth and little pain while tapping teeth. what can it be?

Many things: What you describe can be from many things. The black spots can be cavities, stained pits and grooves, small old amalgam fillings, calculus, etc. The pain on tapping can be from bruxism/clenching teeth, periodontal problems, infections, etc. See your own dentist who can take x-rays, examine you and determine the exact cause(s). We can't do that over the internet.

Tooth decay: You will need to see a dentist who will thoroughly examine your teeth. Dental X-rays will likely need to be taken to evaluate. Tooth decay in pits and fissures on molar teeth can be hard to diagnose and not always easy to see extend of the caries. If you have symptoms I would not wait and see dentist to confirm or rule out cavities.