Sometimes people will frequently remember snippets of things they heard while in surgery, e.g. a joke someone told Some surgeons like to listen to the radio or their favorite music while they operate, so you may very well have heard this song just before you went into surgery, while you were in surgery, or when you were in the recovery room.
It will take a little bit of concentration, but you may be able to block this out on your own. Decide what you want to replace the song with - either specific lines or a passage from another piece of music, lines of poetry or prose, or even a favored mental image. As soon as you realize that the song is "playing" in your mind, concentrate on your replacement. THen say to yourself, "oh, that's nice" (or something affirming like that) and return your concentration to whatever it was you were doing.
With practice you should require less and less effort to switch the image, and hopefully over time the process should become unnecessary.
Hope this helps!
Tre