I don't want to force the issue if he's not ready, but I don't want to wait too long either. You are reading your son's cues correctly. He's probably not quite ready to start toilet training. During your child's check-up, talk with your pediatrician about your child's developmental readiness. Even though your son doesn't sound like he's quite ready to potty train, it's still important to introduce the potty chair and have him become familiar with it.
Toilet training is a gradual process that can take up to three months or more.
As a parent, you can explain what needs to be done, but it's your child's determination that's necessary. When he's ready, it will seem to happen overnight. Your role as a parent is to encourage, reinforce, and praise your son as he is achieving this developmental milestone. There's a large boy on our block who has touched our young girls.