My guinea pig is grinding his teeth?

Ok So i know this is'nt good and i feel horrible..So today i had my guinea pig on my shoulder and he loves sitting there. Well today he jumped off my shoulder and onto the hard wood floors, I Don't remember if he landed on his back. I Asked some friends and they said he could have a broken back, And when i picked him up he started screaming. But he has been running around so i think he is fine. Then i noticed his mouth was bleeding and he must of cut his lip when he fell. But i fed him a cucomber and it was harder for him to eat and it seems like it is really hard for him to drink and i can't open his mouth to see his teeth. all i can hear him doing is grinding his teeth :[