Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concern...
As per your complain and presentation of symptoms the blackening of the tooth along with toothache is due to deep infection in the tooth leading to deep decay which has involved the nerves causing inflammation of the nerves leading to pain..
For this you should
consult a dentist and get evaluated and get an x-ray done so that the exact status of the tooth is ruled out and treatment can be planned..
In case if the tooth can be saved
root canal treatment followed by antibiotics and painkillers will relieve..
In case if the tooth is extensively decayed extraction has to be done..
The other pat of the question is that the black appearance of gums, you need not to worry about it as most commonly the black pigmentation of gums is due to excessive
melanin deposits under the gum mucosa giving it a black appearance and is commonly seen in smokers while at times can be seen in non smokers too..
It is not a harmful condition and does not require and treatment..
Hope this information helps..
Thanks and regards..
Dr.Honey Nandwani Arora..