Hey I am new too, but I have a pig in need of help. I saw some kids throwing a pig in a mud hole in a new housing development. As I drove up they ran into the woods and left the pig in the mud. He was squeaking and I picked him up. Hi front feet seem broken and he just sits there suealing. He is a big fella/gal, not sure, and it cleaned up pretty good in my kitchen sink. I wish I could find the kids that did this.
If it does have a broken foot you need to take it into an exotics vet (regular cat and dog vets do not get much training in the medical care of guinea pigs). They will need to take x-rays to confirm and asses the break. They will also need put him/her on medication for the pain.
For now you need to keep him/her confined to a small space so he/she doesn't make the injury worse. You will also need to go out and get him/her some hay ASAP, guinea pigs need food constantly moving through their digestive system and hay should make up 80% of their diet. He/she may or may not use a water bottle, but with potentially broken bones a dish of water might be hard for it to use.