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How long has this been going on?
Does your cat ever get outside?
Do the nails on that foot look normal?
What exactly has grown? The pad or something on it that you can see?
Or the area that the blood is leaking from?
With the fact that the pad is warmer than the rest I would think he has an infection. Is the infection just from him tearing/catching the pad on something or is there a serious problem under the skin? The fact that he doesn't go outside makes some injuries less likely.
I don't think it is an emergency but I would take him to your veterinarian to have the foot checked. They may want to at least start him on some antibiotics. It is important to make sure something more serious is not going on.
If I can answer anything else please let me know.