I'd agree with the above answer. You may well have developed an allergy, although it sounds quite mild just now. Do you have any eye watering/itching? Any sneezing? If it persists, it might be worth a visit to the docs. If not an allergy, you may just have developed an irritation in the nose lining or sinuses, causing more mucus to be produced. This would respond to treatment with a nasal spray and may well disappear. The piano thing sounds like a nightmare..I'd be tempted to go to the docs just to get rid of that problem alone!