roof leak under shingle

Hi, this is a great forum. My first post.
I've got a leak in my roof. The house is about 8 yrs old. It has leaked only twice so far and only when it really came up a big storm with lots of wind. We've had other storms here where it didn't leak, but there was no wind. I'm pretty sure I've got the leak tracked back to 1 shingle that's further up the roof from where the leak is dripping down into the attic. The questionable shingle is not cemented down as there is a nail underneath the shingle that's sticking up slightly(it's not just the nail head, apparently the roofer bent the nail when he was hammering). Would black plastic cement fix my problem leak? Also, any suggestions on if I should try to pull this nail up or hammer it down more where the shingle will lay flat(I don't want to create a bigger hole, unless there's a good way to fix it)? Also, would this be a temporary fix or semi-permanent?
Any suggestions on this would be greatly appreciated.

Thanks for your help.

 

If you can raise the shingle above that nail without breaking or creasing it, you can either hammer it down or pry it out with a hammer or flat pry bar and replace it.
Smear a good coat of black plastic roofing cement over it either way, and flatten the shingle back down.
Should permanently fix it.
Good luck!
Mike