It is possible that you missed some of the shot (or injected IM/SC) and something is putting pressure on a nerve. If the symptoms don't subside, get worse, or you notice signs of infection or abscess you should seek treatment. Also seek treatment if you just feel you should as you shouldn't let anonymous people on the internet influencing making choices regarding your health and life.
As we aren't doctors and I don't know many that can diagnose you from "Numbeness in arm after injecting" I'm going to close this now as I don't think we can help you any further.
Please feel free to PM me with any questions or concerns.