It would increase the sun's temperature causing it to expand. I guess eventually it would expand out to reach your dyson mirror. Of course there would be all s

It would increase the sun's temperature causing it to expand. I guess eventually it would expand out to reach your dyson mirror. Of course there would be all sorts of secondary effects, lowering the density in the core could slow down the rate of fusion, increased temp would increase it, but no garuntee that the effects would cancel. Also depending on how far out your mirror is the core might not ever notice the change. The outer layers could heat up and destroy your mirror before the increased temperature reaches the core.