Assuming that the physical light switch does indeed report its status to openHAB, this is a perfect situation to apply @bob_dickenson’s Proxy Design pattern documented here
The short version is create a Proxy Item to represent the light. This proxy Item is not bound to anything but it does have one or more rules that trigger when the Proxy is switched. In the rule you can check for certain states and/or set states before triggering the light (or deciding not to trigger the light). So when the light is turned off at the switch you can set a State Item which indicates the motion sensors are overridden; set a timer too to turn the state Item off after a time. Now, when the motion sensor triggers it triggers the rule which checks the State Item before actually turning on the light.