Hi it is completely normal for toddlers of this age to be stressed by, not want to play with, or uninterested by other children - contrary to popular images, children this age don't really have 'friends'. They tend to play alongside other children, not with them - if at all, and that's only because their parents are shoving together in the park. The most common scenario is a 2.5 year old getting a bit stressed by being made to 'play with' another child and will try to hoard their toys (or the other kid's) and cling to or look to familiar adults when they play. They don't have the development in place to seek other children for games or engage with them in any sustained way. Toddlers don't have friends. If They all operate in their own little worlds, sometimes bumping in each others orbit, but not relating to one another in any meaningful way. They relate to mum and other familiar adults, not other kids.
People who say their toddler is very social or has lots of friends at nursery is, with all best will, probably interpreting I have managed to get my toddler to not scream when I leave them with other kids, or he has not poked anyone in the eye for their Paw Patrol car for three days on trot' as 'Eliot is such good friends with Olivia! They love seeing each other do much, isn't it cute!'
If your son isn't at nursery, this behaviour is probably more glaringly apparent to you than it might be for someone who might not be seeing how their child interacts with other children hours at a time. If you work in a nursery, an honest worker will tell you most 2.5 year olds can't stand or ignore other children and tend to focus on an adult (nursery worker) for a a playmate and attention. Older children (3.5 - 4.5) will be relating to other children, bit not a 2.5 year old. Their emotional worlds are quite linear and focused on 'me-other' at this point, which is themselves in relation to another adult figure. It hasn't developed to include other children.
Making and having friends, imaginative play with their own toys, playing with not next to others - these are developments that come a bit later.
A lack of interest in other children at this age or not wanting to play with them is actually quite normal. They might have a passing curiousity in a baby or older children but usually their contemporaries are sources of stress and threats to toys they want and their mum's attention 😂
Boys are slower to develop than girls as well when it comes to language. Being non verbal at that age isn't unheard of for a boy who later goes on to be completely verbal, no problems etc, although it is a point to start making sure there isn't an underlying physiological or otherwise cause.
If there is no underlying cause or nothing apparent, songs, reading rhymes and short rhyming stories as much as you can (although will peck your head in) is good for triggering that sudden 'jump' to verbal in non verbal toddlers
I'd hesitating at offering any diagnosis or 'it sounds like...' online. But you do sound like a great mum who has a lovely little boy. Kids can also be incredibly frustrating and it's frightening to see your kid seemingly going at a slower pace than other children or not behaving in a way you would expect. Tbh if he is interacting with you well, forget about other kids for now, that is the main 'green flag' for a normally developing child. Obviously you need to know and understand what is going on, but you are taking all the right steps to do so. Good luck and maybe get some rhyming sing /song books in and sing / rhyme around house as much as possible - it really is a good trigger for verbal expression 👍 ('here is the washing machine, it makes clothes clean, lalala' )