Should I take it to the dealers? Will i have to pay anything out of my pocket? I don't know how it happened.

 

Most likely a rock hit your fogs while you were driving usually that's the case. Yeah i'd take it to the dealer have them replaced it.

 

umm, no, thats a road hazard, like paint chips on your hood or such. That's all you, though it would be funny to ask a service advisor and watch his reaction.

I recommend spending some time reading what your warranty does and does not cover

 

From the Merriam Webster online dictionary:

Warranty: 3 : a usually written guarantee of the integrity of a product and of the maker's responsibility for the repair or replacement of defective parts

A rock hitting your foglight and cracking it doesn't indicate that it's defective. If it cracked under the heat of the foglight bulb, then it might be covered. Otherwise, external entities that interact with and/or damage it can't be used to show that it was defective. Otherwise, we would probably all throw rocks at our cars whenever we wanted a paint job or new windows or whatever ;-P

And this is a common problem...many TSX's have cracked foglights due to rocks. You'll have to buy a new lense for your foglight which I believe isn't cheap. Once you get a new one, you might look into a light protection product such as those found by one of the forum's vendor, rock blocker or something like that.