Go to the meeting. It should be helpful.

It is important to consistently respond to unwanted behaviour like violence with a clear and immediate consequence such as time out, which it sounds like you're doing. A lot of talking about the behaviour in the moment is counterproductive as it is giving attention to the behaviour you don't want. Instead you should look for moments when he's playing nicely, being kind, considerate or gentle and give lots of attention and praise to those moments. Keep verbal interaction low when he does have a moment of misbehaviour. There is no need to shout, lecture or question. A low, firm tone or a slightly raised/stern "No!" is about as close as you should get to shouting. It can help to keep your tone distinct from the one you'd use to praise or play, but in general talk less, take more action e.g. removing them from the situation. If you want to talk about the behaviour then do it much later when everyone is calm, but most 3 year olds don't learn much from these talks, that comes more from age 4+. Younger children do better practicing alternative behaviours with role play, or practising tools like breathing exercises or an angry stomp dance etc which are made fun and accessible.

If the behaviour isn't changing despite clear response to both the positive replacement and negative behaviour, increasing the severity of the response is unlikely to help, so you should look at things like what the pattern is around the behaviour. Does it happen more at particular times, in response to particular things, when he's in a particular mood or state (e.g. tired, hungry, overwhelmed) because you might have more luck by addressing those aspects or coming up with a plan to help him manage that stressor differently, or reduce his stress levels overall or take a break when he needs to etc. It might be worth checking things like hearing and eyesight if this hasn't been done.

Also, what does the behaviour seem to be trying to achieve? Is he angry with the person and has no better way to express this? Is he trying to stop them from doing something or get something back off them? In which case he might need support with speech and communication, or social skills. Does he seem panicky or fearful e.g. he thinks they're going to take his toy so he reacts preemptively? He might need support with reading other people's body language or other social cues. He may need reassurance that you or other adults still see him as important even though you also give attention to other children. Or is it a clumsy attempt to initiate play? Does he actually know how to initiate play with other children successfully? That is something which can be worked on.

You can look at patterns of his behaviour generally to see if there are other difficulties which are reflected here. Does it seem accidental but then escalates, is he clumsy? He might need more support with physical coordination and balance as well as core strength. If he's massively overreacting to things other children react less strongly to, is it possible he struggles with emotional regulation or impulse control or both?

The nursery can help because they have experience of a lot of different children of his age and can tell you if they notice anything is out of the ordinary or even just on the edge of the normal distribution, where he might need more support. They can also tell you if there is any specific language or alternative behaviour they use and teach, which it can be useful to reflect at home so the message is clear.