I would suggest you cut off about 1/2" from the end of the coil wire and try to screw the spark plug cap back into the spark plug wire. But before you cut the wire, make sure you see a screw inside the spark plug boot. Just make sure that your spark plug cap is still ok first.
Coils rarely go bad, but replacing the spark plug cap and/or cutting off a little from the spark plug wire is fairly common.