Hello sir, Please take him to the dentist and get the teeth filled so that the cavity do not progress to nerve and cause pain to the child.

Hloo Sir Need to see dentist to get them filled so that they do not propagate more

You should take your son to a pedodontist and get his cavities filled.

Since, he is just 3years old you should have much more care because once the cavity goes deep, he will have pain and also the first permanent teeth erupts only in six years... First consult a Dentist and do fillings for the cavities... If the cavities are already deep then you need to do pulp therapy and stainless steel crown over the teeth will be given.. Don't delay, do it asap..