Yes, we have been there...
It happened to DS#2 a week after he turned 3 years old, one of his front teeth was knocked out. His older brother was pushing him in their plastic wagon and they bumped into a wall, which caused DS#2 to fall out of the wagon and onto his teeth. I have never seen so much blood in my life!!!! I wrapped the tooth as instructed and ran to the ped. dentist's office, who said that nothing could be done to save the tooth. The dentist also said that the tooth next to it was loose and that it would probably re-attached itself, but more than likely it would turn grey/brown. At the time, the dentist said that the loose tooth had a greater chance of getting knocked out if another injured occurred. The tooth did re-attach and didn't discolor. However, just as the doctor predicted, DS's previously injured tooth was injured again.
DS (4 at the time) was running, tripped and fell, which pushed the tooth out instead of in.

This time, it looked really bad, as he actually tore a piece of his gum and the tooth was VERY loose.

I ran to the dentist again with DS... When we got to the dentist's office, there was another boy waiting who had knocked out a tooth. Amazingly, this time DS's tooth wasn't knocked out and re-attached itself once again. It turned grey, though.
The dentist said that his permanent teeth would come in and wouldn't be affected in any way. As bad as it looked, he said that when DS's permanent teeth came in, the gum would grow along with it. DS is now 7 and his two permanent teeth have come in. Unfortunately, the gum isn't growing along with the tooth and there appears to be an indentation/bend on the tooth. It's hard to explain, but I just don't know how this is going to be "fixed"or if it can be.
It may work out differently for your DS, though. I was really upset when the injuries happened....

Dentistry has come a long way, so I'm hoping that there will be a "fix" to DS's permanent tooth. Hang in there.