hello and welcome to HCM forum,
i will be glad to inform you that if your child has lost his primary teeth at an age of 5 - 6 years then it is not much of a concern as it is a part of normal growth process.
But if the teeth were lost following trauma of any kind then it might need an attention.
Sometimes a blood clot forms at the site of tooth loss
which gives a purple hue and usually disappears in a 3-5 days. If in case the swelling or the color does not change to normal then i advise you to see a dentist
If possible make your rinse with warm saline 2-3 times/day, it will resolve swelling and pain if present.
i wish you and your son good health.