Such noise is normal, especially when one stays in Flat/Apartment, and one should learn to live with it rather than treating it as a "nuisance". Small children are bound to play and make some noise and one should understand and adjust with it instead of finding fault with it. If you are unable to tolerate such noise, perhaps you should move to another accomodation. As you are worried about your privacy, your neighbour may also be concerned about his child's liberty to enjoy his childhood! However, if you wants to further disturb your privacy and peaceful sleep on this minor issue, you may resort to legal actions too.