I have pain in my left jaw bone i feel it overlaps and gives pain when eating. i have a deep cavity in my left end tooth. what does the pain due to. ?

Infection: Your pain co-relates with your cavity and a dental infection is the most likely cause. Would recommend you seeing a dentist at the earliest for both antibiotics and then further management, possibly including a root canal.

Root canal infection: Likely it is an infection in the bone supporting the cavitated tooth. Once the cavity reaches the nerve and blood supply inside the tooth, it travels quickly inside a root canal of the tooth into the bone. If the tooth is not decayed terribly, then it can be restored after a root canal treatment. Root canal treatment will likely eliminate the cause of infection and pain.

Your cavity: Your pain sounds like it has a very high probability of being due to the cavity in your tooth. See your dentist and have it checked and treated. This is a very common scenario that often leads to a root canal or tooth extraction.