2005 Mustang door ajar light stuck on

not sure if its related, but i pulled my rear bumper off over the weekend looking for a water leak in my trunk.( i think i found it but time will tell). anyway, for the last 2 days my red door ajar light on the dash is lit, and i keep getting the bing,bing,bing every minute or so. i dont know why its going off, doors and trunk are closed good. i havent hooked the tuner to it to see what that says yet.