Should I cut this leaf off?

[AnitaPita]

Hi! One leaf on my plant had a black spot when I received it as a gift. The spot was black and dry, with some yellow around it. Now the blooms have fallen off, a new leaf is sprouting at the bottom but the black and yellow is spreading just on this one leaf. Should I cut it off? The person who gave it to me said the girl at the floral shop told her it could be cut off. I have attached a pic...sorry for the bad lighting.

Also, I've seen some say to cut the shoot off below the last node and some say don't. If it's going to bloom again on that same shoot, how long will it take? If I cut it off, do I need to put something on the area where I cut it?

Thanks so much...