Hi there ....yes...certainly its because of bottle/breast feeding at night popularly called as nursing bottle decay... It will disappear once the teeth sheds and he gets the new set of teeth.. But..!!! If the infection is active, it might spread to the underlying developing permanent tooth buds...which may lead to brown or blackish discoloration of the future permanent teeth...and many more sequels.. So I would suggest ...please visit your nearest pediatric dentist and get it corrected ASAP ... Once there is no active infection ...you can opt for few preventive measures in order to prevent the future cavities. .. Take care ...!!

Your son will definitely get his permanent front teeth when he will be about 6-7 yrs old. But till then you need to make sure that all of his existing milk teeth are properly cleaned and brushed everyday. At the same time, you have to visit a pediatric dentist for treatment of the already carious damaged teeth. Broken tooth structure can be replaced by giving Caps/crowns.