Has anything happened to shake his trust in humans?
I would move slowly with him, handfeed him treats, not walk directly towards him, and watch my body language around him. He might be thinking he's being aggressively approached when in fact you're just walking about minding your own.
There's a chance this is only a temporary phase due to puberty, but if it persists and he won't tame again despite your efforts, then he might not be great breeding stock unless you don't mind working with flighty poultry. Some don't mind, but I do.
Some chickens are human-averse without due cause from a young age, some others adopt that mentality as they grow. I don't appreciate it, since a spacky chicken tends to breed more of its sort which makes it hard to handle and treat the individual as well as running a risk of that bird inciting others to panic around humans. I've had the occasional rooster that I've culled for making the 'beware' and 'predator' alarm vocalizations whenever I approached the coop or the flock. A human-averse bird can turn friendly ones against you. It makes tending the flock difficult, which is a risk to their well-being.
I would work on regaining his trust and friendliness and hopefully he'll settle down again.
Best wishes.