How is ozone formed in the uppermost atmosphere? Why is damage to ozone layer a cause of concern to us? What causes this damage?

Oxygen molecule splits into atomic oxygen (O) at higher levels of an atmosphere because of higher energy of UV radiations.

So, $O_2⟶O+O$

$O_2+O⟶O_3$ (Ozone)

Damage to the ozone layer is a cause of concern to us as it forms a layer in the atmosphere which protects us from the harmful UV radiation.

Damage to ozone layer can cause penetration of UV rays in the earth surface which damages human organs, plants, etc.