changed my rear brake bulb today, now filler cap and central locking aren't working properly?

i have checked the outer fuse board and everything seams fine, i can't get at relay board (not that confident) i am low on petrol... the issue arose literally straight after i changed the rear brake light on the drivers side....very low on petrol... is there a way to get petrol in first of all... then i'll worry about central locking.....