I coach a lot of youth lifters, including my own children. My thoughts are, he hit a PR, so end on a good note.
Does he have specific goals? Going to a national meet? A specific snatch or clean and jerk goal?
I have found that I fail miserably any time I try to push my daughter, but I've realized that she only lifts for fun and when she wants to and isn't dead set on competing. So, I let her do what she wants and if the opportunity presents itself, I encourage her to push a little harder. On the other hand, my son is VERY motivated by hitting PRs and is much better at being coached by me when the going gets rough.
I think the key is making sure that his goals are his goals and not your goals.
My coach, Jim Moser, coaches all youth/teen lifters. If your son likes watching videos of other younger lifters, his YouTube channel would be a good one to follow.
With my own kids, I find that it is important to have very specific goals for each training session when they actively need me to coach them (sometimes they just lift without coaching). Otherwise, it turns into a train wreck. But, my kids are also much younger.