I have had implanon inserted a few months ago, and had to have it removed a week later due to infection and large pain & numbness in my left arm and fingers.  The numbness and tingling & weakness is still present, especially around the elbow area - the implanon was inserted into the elecranon (elbow), just underneath my elbow.
Hi, Paresthesia is possible after insertion of Implant although very rare. As you told it has been few months since removal of implant and still you are having numbness. Here I would suggest you to go for Nerve conduction studies and in the meantime you can start multivitamin capsules single per day.