Gil,
This is not a part of the body you want tingling without certain stimulus.
Though it could be swelling or something else on the minor side, it could also be the start of something new or ????
Does changing positions help (no pun intended), sitting up, standing, leg draped one way or another? Does any part of you back hurt with this tingling? Have you tried icing down your back?
Since nerves are funny, ganglion things and not enough is known about them, rather than risk something permanant, if this doesn't resolve in a very short period of time, I'd head to the doctor.
Good luck, Dale