Hello.... One should move his fingers within cast.. Otherwise it would be difficult to move fingers after removal of cast... Try to move fingers in possible range... Get an x ray of hand to see if it's healed completely or not ... Consult physiotherapist in nearest hospital... ..
1.Bend your fingers and extend it repeat this for 20 repetations.
2.Sqeez a towel/ball/edge of pillow which ever is available, hold for 5secs and release repeat this exercise for 20 repetations.
3. move your wirst in clock wise and anticlock wise direction for 10 reps each.
If you experience any pain or swelling post exercise you can do ice fomentation(dip your hand in ice water)for few mins this will relieve your pain.
you can start all these exercises as a home remedies. and if the stiffness still persists visit your nearest physiotherapy centre.