Nato will not get involved inside the Ukraine because ukraine is not a member of nato
many people think that NATO is some humanitarian group helping out any country in need. but they are not. they are a member service, helping out only those that are members. (just like a gym membership)
This is not always the case. For example, in 1999, NATO bombed Serbia during the Serbian aggression on Kosovo in the former Yugoslavia. The NATO offensive came as a result of a wave of ethnic cleansing committed by Serb forces against the Albanian majority in Kosovo.