Hopefully your port has been stored horizontally - to keep the cork moist. Also, it should have a white (or some colour) mark on the bottle to indicate that it has not been turned, as a sediment may form and it would be preferable for the sediment to settle firmly in one place at the bottom of the bottle. I would recommend that the bottle is VERY gently handled, opened and decanted (avoiding the sediment) into a new clean bottle or decanter before drinking. Hope this helps.
Cheers, Andy