Hi. Before I can comment anything, I need to know many other aspects of the child.. Eg what about left leg? What about upper limbs? What about his milestones like walking, talking etc? Spasticity indicates that the child has some problem in the brain which causes the leg to become stiff. Spasticity needs physiotherapy to make the leg supple again and other medicines if needed.
Next Steps
Pls see a Pediatric Neurologist