I warmly Welcome you! Thanks for consulting at my virtual clinic HCM, the best team of online physicians. Yes, it happens accidentally or due to inexperienced hands. But there isn t any specific time period defined for relief from pain due to the fact that every incident differs in & depends on: *What was the medication in injection thay got wrongly intonthe nerve. *How much of the amount went in the nerve. *Which nerve specifically involved. Definitely, the pain goes to the area supplied by the nerve past the injection site. It isn t felt on the site of injection. If injection goes into a wrong muscular or facial compartment or it slips the vein and spillage of the blood or the medication into these spaces happens then pain and swelling is seen on the site of injection. Such accidentally injected medication induced nerve pain may take weeks to months to resolve completely. Hope I answered your concerns completely. But its always difficult to cover all doubts in a single query. So if you have any further questions please feel free to contact me back anytime. I am available to get back to you in no time. Regards! DR.HANIF USA