If the output of the SHA256 is greater than n it will just "wrap around" and work.
Although, now that I think about it, if the output of your SHA256 was exactly n that would probably cause a problem.
But then, the probablity of the output of the SHA256 being exactly n is 1 / 2256.
You should not "wrap around" or reduce your integer modulo n.
If your integer is == 0 or or >= n, then you should discard it completely and generate a new private key using a new secret. Otherwise you would be introducing a bias towards lower-valued private keys.