of course it's okay to continue BF! probably the best protection and medicine in the entire world for your LO...
as for medicine, you should always ask your dr., but they will generally tell you that most things that are made with a children's formulation should be okay-- or, believe it or not, take the children's flu meds. like i said, i'm no dr., you should ask someone that went to medical school, but MOST things are actually okay. just be careful about anything that "dries up" mucus, because mucus, sweat, and breastmilk are all produced in a similar way by the body, so although your nose may be un-stuffed, your milk production may suffer as well.