You shouldn’t restrict your child’s movements. You can do your best at soundproofing, which you have with mats etc. Outside of that, this is normal behaviour and you don’t owe anything extra to your neighbours.
It's just part of living in a flat. My daughter can be noisy and jump around etc, but in turn my neighbours also will cheer loudly at football games, and run the washing machine at midnight haha. People have the right to do what they wish within their property, we can try to be respectful of others and to teach our kids to be, but your home should feel like a safe space for them also. Having carpet with underlay provides some insulation
I should also add he's on nursery 4 days a week, so it's happening only 5% of the day ish, mainly evenings.