Hi dewslat, I am dental student myself, This is not a problem to worry much as the tooth is not infected(main sign will be pain when it happens) But I will advice you to take him to dental surgeon (pedo specialist not needed) as the tooth requires pulpectomy(root canal treatment) as it may lead to deformation in growth and eruption of permanent tooth below it. I hope you were in India - treatments here cost equal to One meal (we do Root canal treatments for 10$ max )