There's a thread on here somewhere in which the OP is modifying his headlamps. I don't remember if he was "upgrading" his headlights (HID??), or just changing the "color". I do remember that he was going for a change from chrome to black or vice versa in the look around the edge of the headlamp assembly (I think he was going for black to match a "darkened" theme in his overall appearance.. which replaces clear sealant with black???. In fact, if I remember correctly, one of the things he might have done was to change (tinted) the reflector inside the assembly???
Anyway, one of the things he shows is how to separate the 'lens' face from the rest of the assembly, and then reseal the lens to reattach. It involved using a heat gun I believe.
So if you can find that thread, you'll have some great instruction to follow with respect to resealing your lens, if that's where your leak is.
If you don't want to go to all that trouble, I'd see if you can't just put a small bead of clear silicon sealant just behind & all around the outside edge of the face ("lens") to re-establish a good seal with the 'body' of the headlamp assembly... without creating an ugly mess??. Of course only do this after you have sufficiently dried out your assembly.