you may have just popped the safety cover on the control cable

it's got a little red tab which sometimes comes adrift which means that you can't open the door from the inside as the handle won't allow enough movement

if it's only the drivers door you can't open from the inside then this will almost certainly be the culprit

the cable is about £8 from ford, just be careful when fitting it as the plastic can easily snap, rendering your new purchase useless

if it's just general door locking issues regarding the central locking then you will find it's almost certainly the central door locking module, built into the drivers door lock assembly

replacement is the only viable solution, either second hand or new, second hand is much cheaper and easily doable with a set of screwdrivers and some small pointy metal prongs