And, welcome to YT
Some teeth can take up to a year or more to fall out by themselves. Most Veterinarians will pull retained teeth at the time of a spay or neuter. And, if you're not planning on neutering him, I'd discuss the extraction with your Veterinarian when your little guy is scheduled for his annual exam if it hasn't fallen out on its own. Until then, you can work on it yourself and just maybe save the extraction expense. Wiggle it, play tug of war with his favorite toy, etc.