I've seen a few people with similar questions. What I understand is in new born infants TSH tends to rise then fall as the thyroid starts working. Some babies this may take a little longer than usual. So it's likely this will resolve by itself.
If not then the cause would need to be found and treatment (thyroid meds) started. I think prognosis is generally good so don't be scared.
The doctors at the hospital will know more about this than anyone here though.
They always test thyroid levels in the hospital almost immediately after birth to ensure immediate treatment should the infant be abnormal. What were the results then? Do you have access to that info?
Was your son also tested for the actual thyroid hormones, Free T3 and Free T4? If not, he should be.
TSH levels are, typically, higher in infants; what was the range given on the lab report?
Your son must have adequate thyroid hormones in order to grow and develop normally; treatment is just as effective and necessary in infants, as it is in adults.