If a child of 16 months old has white bumps in their mouth, it is important to monitor the situation closely. These white bumps can sometimes be indicative of a fungal infection, such as thrush. It is recommended to keep an eye on the symptoms and if they persist for several days or if the child's general condition worsens (fever, pain, decreased appetite, etc.), it would be wise to consult a doctor for evaluation and potential treatment. In some cases, white bumps in the mouth could be a side effect of a recent vaccine, in which case they should improve within 24 to 48 hours. It is always best to seek professional medical advice for proper diagnosis and treatment.