Hello Jimages,
Could you tell us if, a part from the localised stiffness on neck and shoulders, you have experienced any other kind of symptoms such as headache, pins and needles or even numbness radiating in part of you right arm? Could you remember if you did any particular movement which gave you this muscle pulling in the neck/shoulder? What about your range of motion in your neck? Can you put your chin to your chest? Do you have any difficulty in turning your head to the right/left (you should be able to have your chin almost parallel with the shoulder, looking over it)? Any restriction in lateral flexion? Is there anything that make you feel your neck better or worse? Do you have daily pattern in pain or stiffness of your neck/shoulder?
for what concern your thigh, how did you injury it?
Be careful with excercise at gym, strenghten a muscle does not mean always support and give relieve to a joint.
Regards
Emanuele