My Guinea Pig has an open sore on back foot and his back feet look like blood blisters Why?

My 6 year old Guinea Pig has an open sore that is covered by a flap of broken skin or pad? If I lift the flap it it looks so raw and red. Almost like it is going to bleed any moment. His cage is always clean and I use cage soft bedding. Both his back feet look like blood blisters. He is eating well but today it looks like has lost some weight. The sore concerns me a lot. What can I put on it? Should I rinse it in peroxide? Use a triple antibiotic or Iodine on it? I read something about saline solution maybe? I will take him to vet tomorrow but I want to do something for him now. Any help out there is very much appreciated.