Aware of Social Skills but Won't Use Them

So my son is level 1, super verbal, and is very aware of what proper social skills are. But he won't actually use them. He has been in social skills play group for 2 years (age 3.5 to 5.5 currently), and we talk about it a lot as home as well. But when it comes to actually *using* them in real life settings, we have made zero progress. For example, he knows that if your friend falls and gets hurt, it is kind of ask if they are okay. But he just. Won't. Do it.

Over the weekend we were with his closest friend and he had a fall that required a few band aids. I encouraged my son to ask if he is ok, but he refused and started crying instead. We talked about it later when things were calm. He said he is too nervous to ask "are you ok" to his best friend. I asked him what he is nervous about. He cried and hid under a blanket and wouldn't speak to me.

We had a similar reaction last week when I suggested he say "good job" to his friend for earning the next level karate belt in their class.

Long story short - my son knows what he is supposed to say. He won't do it. Says he is too nervous. And I can't get more out of him than that. Any help please?!