Do I need to fix the sealant on this window?

[SharonInBelfast]

I've realised that the paint on one of my exterior windowsills is flaky and loose. Some of it has already come away, and I'm planing to scrape the rest off to repaint. The window has obviously been sealed when it was put in, but the sealant is on top of the paint, so where the paint has flaked off, there's a small gap (couple of mm) between the sealant and the windowsill. Obviously if I scrape the rest of the paint off, there'll be a gap the whole way along.

What should I do about this? Put some kind of sealant into the gap? If so, what kind? Or would it be enough to just kind of paint over the gap (and poke enough paint in there to fill it)?

The window is uPVC, and the sill is concrete (I think).

Thanks for any advice!