If you are talking about a therapeutic nerve block, in a matter of hours, you will feel better. But in a week, it will go down until is disappears.

It depends on the medication used in the block and what block was performed. Anywhere from a couple of hours to 36 hours.

That depends on the type of medication used (medications have different length of effectiveness), how accurately it was placed (ultrasound guided blocks have the best accuracy of targeting the nerves needing to be blocked) and if a catheter was placed to prolong the duration but delivering a predetermined amount off numbing medicine to your nerve.