there is water inside the front light of my car ?

i have found what looks like condensation in the ofside front light of my car and yet their does not appear to be any sign of cracks in the glass ?? i am puzzled as to how it got there.
i spoke to the garage were i bought the car and he said that once i use my head lights it will dry out.
please can any one come up with the answer as to what i must do.
thanking you.
Reg.