Tmi secretion from nipples

Hi friends sorry for tmi.. I am  24 weeks now. Today when i checked my boobs before applying bio oil my nipples felt dry and cracked and when i tried to check got little transparent secretion out. Is this normal. A month back when i was on holiday on mount Washington my nipples  hurt like crazy coz of the cold there. My doctor suggested that i keep it moisturized and she said something about stimulating. I didn't quite get her. What am i supposed to do. How else do i maintain. I hate that my nipples have turned darker hope they come back to normal later. I am a ftm.. Please excuse my ignorance N helpp