Hello and welcome. Thank you for requesting me. I apologize for the delay. I was not online at the time you posted your question, and am not sure why I was being shown as online. I just logged on and saw your question. I'm sorry to hear of this problem.
From what you have described, your Guinea pig is probably suffering from pododermatitis, commonly called bumblefoot. It usually begins with a slight injury, and then infection sets in. This may not sound extremely serious, but it is. It is a common cause of death in guinea pigs if it isn't treated. The best thing you can do is make an appointment with a vet familiar with guinea pigs. Here is a link to directory that will help you find one near you:
In the meantime, if your guinea pig is on a wire floor, move herto an enclosure with a solid floor. Wire cage bottoms are one of the causes of the foot injuries that lead to bumblefoot. A fish tank works well. If you can't get one, you can use a cardboard box temporarily. Just keep an eye on it to be sure she isn't chewing her way out. You could also put cardboard over the entire bottom of her present cage. It's very important that the bedding be kept dry and clean. This site has much more information on bumblefoot, including supportive treatments you can do at home to supplement what your vet prescribes:
It would be good to read everything at the above link.
If you have more questions, let me know in a REPLY. I hope your guinea pig will reacha full recovery.
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