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Does it look like a spur of dead skin? They are very common but don't need anything doing about unless they really get in the way. In that case, please either let your vet cut it back or be careful to not cut too close to live skin. Guinea Lynx :: Guinea Pig Feet and Foot Problems
They don't go away by themselves unless they get caught on something and rip off with the risk of bleeding etc. They can and should be trimmed with nail scissors but not to close to the skin in case the skin is nicked.
It's definitely a foot spur. Some pigs get them and others don't. They don't do any harm, although you can trim them back with nail clippers if they get long enough to get caught on things. Sundae gets them and honestly I just leave them alone, as getting them trimmed stresses her out and they don't get caught on anything or bother her.