Failure to achieve developmental milestones may be due to variety of causes.
In your case, as birth and perinatal history is not known, it is difficult to predict the cause.
But you should visit pediatritian / Neuro-developmental specialist immediately to find the cause and start necessary treatments.
Causes may be nutritional deficiencies, premature birth
, birth asphyxia
, maternal or neonatal infections etc.
Most of the time, the child needs long term follow up and managements like self-care training,social development and speech therapy
,gross and fine motor training, sensory regulation,communication skills training etc. Neuro-developmental follow up - is a recent wing in extended Neonatology
a very few centers have the facilities. However, I would suggest you to choose a near-by / conveniently accessible clinic as the child may need long term follow up. Treatment should be started as early as possible as early management has better prognosis.