About all you can do is to hand route the affected area then enter those nets into the Autorouter in the Skip Nets section.

Thank you for a quick reply!

Another possibility might be to place all your components but place those in the affected area further apart to make routing easier. That might be enough on its own but if not you could start the same way but temporarily cut all except those in the affected area and run the autorouter. Then paste the cut parts back whilst cutting the routed area and run the auto router again. Lastly paste the original routed are back and then sort out the routing between the two areas by hand.