Not usually. One hopes to have decreased pain and relief of symptoms after the injection. Numbness in the area described may be what's called saddle anesthesia. This is named for the area that comes in contact with a saddle when sitting on a horse.
It may be a sign that the disc is putting too much pressure on the spinal nerves inside the spinal canal. The area of nerves controlling bowel and bladder function is called the cauda equina or "horse's tail." It's the lower end of the spinal cord where all the final nerves come together and go down as a bundle.
Call your doctor and report these new symptoms. You may need immediate treatment to prevent long-term problems.