We will work backwards in your situation.
1. You had a back injury
December 2012 and 2 vertebrae were bruised (no details of specific vertebrae mentioned, doesn't matter). You have not told of any resulting disc herniation at that time. There is no reason disc herniation will occur now just because of sitting down for the past 3 -4 weeks.
2. Tingling sensation
in your vagina could be entirely due to a small infection in the area because of your sitting down for a long time. Please visit washroom regularly and if things still dont improve, you may consult a gynaecologist for medication.