My 9 month old lab threw up a good sized rock in the middle of the night. He seems to be fine now but should I be concerned about anything internal that may have been hurt?

If he isn't showing any other signs of distress, likely it didn't hurt anything. Keep an eye on him. Anything much different from usual and call the vet. Dark, tarry stools is a sure sign of internal bleeding and would mean call the vet.

I have seen an exhibit of things surgically removed for dogs at the dog guide school clinic. The collection includes several rocks. At a talk last summer, we were warned not to let the dogs eat bottle caps. The sharp edges will cut up their insides.

Hi,
Just to reassure you, it's probably OK. Dogs will "eat" most anything, and as said, if not sharp, should be no problem.
My neighbors Husky ate a wrench,. small one. Amazingly enough, he threw it up the next day.