S.G.
DON'T WORRY! And don't pull the baby ones out. The same thing happened to my son when he was 5. I was shocked when I first looked and saw them coming in behind his front bottom teeth. It looked like they were coming in under his tongue. His baby teeth in front were not even loose. Believe it or not...they will get loose in time and fall out and the other ones will come into place. Don't pull the baby teeth.
Good Luck,
S.