Thanks for posting your query.
The hanging deciduous tooth which has retained in your son"s mouth has to be removed as soon as possible.
Please do visit your dentist
As the procedure is carried out under administration of local anaethetic solution,the procedure will be painless.
Take complete course of antibiotics-analgesics too.
Gargle frequently using warm saline and betadine
Please do get a dental check-up in every 6 months.