It it still drives straight, you probably didn't do in the alignment (not a surprise on an XJ, which holds its alignment well), but it might be off just enough to nibble at a tire edge and cause wobble. "No visible damage" obviously isn't enough. You need now to find the invisible damage. First off, you could have lost an inside wheel weight and not know it. Second, it could have bent the wheel, and you need to check that. Finally, it could have caused a tread separation in the tire, which doesn't necessarily show, but will cause wobble and could of course also blow out and depending on the circumstances do anything from inconveniencing you on a hot day to having the troopers pick you off the road with a snow shovel, so you'd better have it looked at.
First thing I'd do is jack up the wheel and give it a spin and look for any runout in either the wheel or the tire. If none, the next step would be to swap the front and rear and see if the wobble changes. If it does, I'd have that tire looked at for internal damage. If it doesn't it's alignment time.