I had a very mild groin strain a few months ago. I was fine after about a week, but the grade of strains is a big factor in recovery. Lot of good info can be found through a simple google search for "groin strain recovery" to answer general questions. I'd give it a week minimum, but they can take as long as a few months.
http://sportsmedicine.about.com/cs/hip_groin/a/hip2.htm
http://orthopedics.about.com/cs/spra...instrain_2.htm
http://www.m.webmd.com/fitness-exercise/groin-pull