I'm not a legal expert and fair use is a widely disputed topic, even in the courts. I can understand the dilemma. If it was a story about the song, it may fall under fair use, but I can only recommend that you seek legal advice if you want to be sure. If you're a member of the Society of Authors they have a legal team that may be able to answer the question. As Writers' Digest say, it's often said that you need permission for even one line. So, personally, I always try to err on the side of caution.