It seems that in Matthew 15:24 Jesus is saying his focus while in the flesh was on his own biological people. Perhaps this is because he was only to be in public ministry for a short time which we know to be three years.
Matthew 15:21-28 clearly speaks of a Canaanite woman who was a non-Israelite. We know she is a non-Israelite because Christ tells us so in Matthew 15:24 else his statement to her would be of no value in the context of the conversation.
So although his primary focus was on the house of Israel, Christ did not turn this non-Israelite away.
We see this same principle in Luke 24:47 and Acts 1:8 as to beginning in Jerusalem and extending to the world turning neither Israelite nor non-Israelite away.
Indeed Matthew 28:18-20; John 3:16; Romans 1:16 are example scriptures that though Christ in the flesh seemingly did not geographically go other than to the house of Israel, Christ himself did send his disciples then and now to Israelites and non-Israelites worldwide.
Indeed, Jesus Christ says he is for whosoever will come to him (Matthew 11:28-30 and Revelation 3:20).