Do we need sunblock if the ozone layer is healed?

We still need it, as the damaging UV light isn't fully blocked just mostly absorbed. Most of the UV-C light is blocked, which can cause serious damage. Then there is UV-B and UV-A. They all can cause sunburn and some of it will still reach the surface.

The desity of the ozone layer is also dependent on many parameters and not homgenous. You still have different exposure szenarious, depending on altitude and geographic location.

We could use less and hopefully see much less skin cancer in the coming decades.

Did sunburn exist before we damaged the ozone layer?

Have people been using various substances and mechanisms for sun protection for thousands of years?