I would not give the puppy any medication right now, people meds are not necessarily safe for dogs, pain-killers especially. They should ask the kids if they know what happened, but keep an eye on the pup and see if it gets better after he sleeps some. Pups often pull muscles or twist things that might heal on their own, but if it seems to really be in pain, you can call an emergency vet and ask them what would be safe. They can give you more guidance, especially as they will know what is safe and what dosage a puppy of his size can take. She should weigh the pup, as they will likely ask for that info!

Here is the number for Angell Memorial, it is in Boston, near me, but they will answer calls from anywhere, and have people on staff 24 hours a day for such matters! 617-522-7282 (press 1)