What Causes Protruded Vein Post Having Nexplanon Implant In Arm?

Hello i need help please i dont know what to do. I got thd nexplanon inserted 3 weeks ago the first week was ok a little bruised but then i had pain and a hard time stretching my arm out all the way you can see like my nerve pop out not letting me stretch it fully and i get this bad pain all down to my wrist. What has happend?