My tooth is left untreated for years amd looks its decaying.no pain but feel i little numbness in the cheek.there is no other issue.can it be serious?

Yes: It sounds like you haven't seen a dentist for while now. This may or may not be a serious condition and you need to see a dentist as soon as possible for a proper diagnosis and treatment. Hope that helps.

Numbness = Issue: Possible infection that is spreading. High blood pressure, diabetes, and many other illnesses have no pain but can kill you. Please see a dentist immediately.

Fortunate: You're fortunate you have not had acute symptoms. I would, however, be very concerned about your infection induced numbness. Infection can cause bone/gum loss, permanent nerve damage, blood pressure increase, diabetes, and other problems. Stop hiding from reality. See a Dentist immediately.

Yes: If there is numbness, then it can be a serious problem. This means that your nerve supplying the feeling to your cheek is being affected. See the Dentist right away for examination and treatment. Do not wait. Good Luck.

Yes: See a dentist ASAP. Where there is numbness there is a compromised I the nerve. Find out what is going on. It will not get better without treatment.