In the best case, the aircraft would not be able top pressurise and would simply turn back.
Worst case: As the Cabin Pressure is initiated and stress builds around the holes they could tear open into even bigger holes… with the rush of air from being inflight then tearing the plane apart.

This is what happened to Pan Am 103. The Bomb blew a hole in the fuselage and the rush of air ripped the plane apart.

PAN AM 103 was pressurised before the side was blown out , if somebody holes the presssure cabin on the ground the pilots will get a warning that the cabin is not pressurising AFTER TAKE OFF and they simply have to land , the plane doe’s not pressurise fast enough to cause any damage via existing holes – it just wont pressurise at all .

Al