Most regulators cap the voltage 14.5V, so you are well outside of spec. Running with that amount of excess voltage can eventually burn out bulbs and other electrical components so you need to get it fixed ASAP.

I had the same problem on my 98 Accord and it was cranking out 16V. I changed the alternator the next day and didn't have any adverse effects.

On your car the volatge regulator is inside the alternator, so he is at least going to have to pull the aternator to fix it.