Ground plane and an impedance-controlled signal trace
Yes you will have an impedance discontinuity there.  You should also look at how the return current is going to flow where you have that via.    That's another discontinuity there current travels in a loop so I would think about having a return path there.   Don't know what your bottom layer is though.

Trying to find the impedance all the way through that structure would probably require a field solver.   Personally I'd avoid the via if you can.  My guess isn't will increase your insertion loss.

On the other hand that via is close (less than 1/4 wave length) to the connector so it will get lumped together with it.