How long before sciatic nerve pain from injection goes away?

Several days: Epidural steroid injections have used since the early 1950s to treat lower back & radicular pain. It is generally accepted that they provide short term relief of symptoms in at least 50% of cases, there is still no good studies to substantiate long term effect. There may several days of increased pain initially because of increase of pressure from the injected fluid or due to local irritation.

Normal: If it does not resolve in a week, call your doctor to see what options you may have regarding this increased pain. Although uncommon, it can happen and usually will go away on its own in a few days.