Whats wrong with my fish? looks like its dying but i dont think it is..?

I have a guppy and its a female. its probably around two months old. im not really sure cause i have so many. buuuuut, i noticed about a week ago it has a tear through its tail im guessing from my colored tetra biting it and then it started to tilt upwards. now it can barely swim and its on its back. however it still eats and swims upside down on the floor of the fish tank. it has been like this for 3 days and i looks healthy its not losing color or anything. is it dying or is now handicapped or what? just curious...