My son is 14 year old boy.at 7 years old he had a head injury on the back, he didn't pass out so i didn't go to the er. he's in puberty and he's scared he is never going to get tall, as recorded he only grew 1 inch from 13-14. should i see a doctor?

Your best reference remains his pediatrician who would be able to plot his annual growth against peers his age. There is high variability in puberty as growth happens in spurts.

I doubt that a minor back injury has anything to do with his growth. If he only grew an inch in the past year he is likely near the end of growing taller. A single x-ray of his wrist/hand can detect open growth centers in his bones. If wide open he can grow taller, if closing he is near the end. If closed he is done. No diet/exercise or meds can change growth after growth centers close.