Thank you for your query on Healthcare Magic,
Your child seems to have a nodular goitre
which is common around pubertal age.
But evaluation is required to assess the thyroid function with T3,T4, and TSH, ultrasound
of the thyroid to know the type of swelling.
Dont worry about thyroid cancer
as it is very rare.
Consult your Pediatrician
for further evaluation and treatment.
Hope I have answered your query, if you have any clarification in future please feel free to consult me.