Thanks for sharing your concern.
could be due to periodontal infection
,especially in diabetic patients.
There are other reasons too for tooth ache like decay,gum infection
,any trauma causing fracture
please visit your dentist
once for oral checkup and then if required you can get the concerned tooth extracted,if the prognosis is not good.
I am suggesting you extraction for the sole reason that i am suspecting a loose tooth in his mouth due to diabetic condition.
Exact diagnosis can be done only upon evaluation.
There are many charitable camps organized,for which you can check on net in your area and get the treatment done.
Another, better option available is you can visit any of the dental schools ,where students are doing treatment at a very nominal rates .
This treatment is also done under doctors supervision.therefore you can approach there.
Hope it helps.