'Stuck valve' is a general term. Its the valve bent? Is the guide damaged? Is there rust/debris interfering with the stem? Is the valve welded to the seat?
Could be anything... best bet it to take the time to fix it. It won't get better magically... it may work for a while, but wear is wear. Plus once the head is off you may find other issues that make the motor a keeper or junker.
Plus if it is not moving you have a rocker, push rod, tappet and cam lobe that are getting damaged as the motor rotates. If you are lucky you simply bend a push rod. Worse case? Wipe a lobe, snap a rocker, put a valve through a piston etc etc etc
