It sounds like he’s trying to maintain control of a situation he’s uncomfortable in. You’re on track with working on social skills. Just remember, in an overwhelming and uncomfortable situation he will not have as much cognitive control to recall and use what he’s learned about social situations, at least at first. It will take time and consistency to make the appropriate behavior more natural for him.
Here’s more on teaching kids with ADHD social skills:
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism