I would have handled it the same way. The level at your son's age, kids usually parallel play, which is less interaction together. As your son ages, they start interacting around 2-3 years old.
I found this for 12 month development hope this helps:
When Parallel Play Becomes Playing Together
Babies play side-by-side, but older toddlers move beyond parallel play to really interact with their classmates and playgroup buddies.
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Next time you’re at the playground, take note of how the toddlers interact. Chances are, if they aren’t grabbing, hitting, or throwing something, they’re totally ignoring their playmates or, at best, grunting in one another’s general direction. Pretty antisocial, huh? Yes — and perfectly normal, especially for young toddlers, for whom parallel play (playing side-by-side, with no interaction) is still the name of the game. But the tide is about to turn, Mom; at two to three years old, kids start to notice one another at play and to share their stuff (hallelujah!) in loosely organized ways (this is called associative play).
During parallel play, babies and toddlers sit happily alongside one another but rarely interact. One critter may occasionally look up from her shape sorter to see what her pal is doing or even to hand her a toy, but more typically she’ll spend most of her time in her own little zone. Yet that doesn’t mean she doesn’t enjoy being around other toddlers — in fact, she loves looking at faces and bodies similar in size to her own.
When associative play emerges, toddlers begin to share playthings. Your toddler and her playgroup gang may all build with blocks, for example, but each constructs her own teetering tower. Or they may all cluster near a play kitchen, busily “washing” their dirty dishes or stirring an empty pot — but without the planning and directing (“You be the mommy and I’ll be the daddy”) you’ll see among older kids.
Of course, all this associating is bound to lead to squabbling, since toddlers this age are still learning about turn-taking, sharing, and the many nuances of “being a good friend” (some adults are still working on that!). You can foster friendship skills by trying these tactics:
Be a good role model. When you play with your tot, make a point of asking before picking up a toy she’s been using. Once she gives you the green light, tell her you appreciate her giving you a turn and praise her willingness to share. (Oh, and don’t forget your pleases and thank-yous.)
Choose cooperative games. If you’re hosting a group (or even just a pair) of toddlers, make ring-around-the-rosy or other circle games part of the fun, or have them roll a ball to one another (a great way to teach turn-taking). All-hands-on-deck activities such as cooking together, doing crafts, or making music encourage teamwork and sharing.
Intervene when necessary. Keep a close eye on toddlers during playdates and be ready to step in quickly if anyone’s on the verge of lashing out. With all the matter-of-factness you can muster (whether your child is the aggressor or the victim), separate the battling parties and redirect them to a new activity or separate areas of the room.
Practice…a lot. Just because one playdate (or several) ends in tears and tantrums, don’t give up. Learning social skills takes time. Experiment with different groups, settings, times of day, and activities (without overstuffing your child’s social calendar, of course).