Depending on why the hood won't open, there are a couple of things you can do. If the latch is activating when you pull the handle, you can slap the hood beside the latch, and it may jar it loose. Slamming your door may also jar it loose.
If the latch is not working when you pull the handle, you may have to remove the grille, and try activating it from the front.
If the grille can not be removed, you may have to work from the bottom to release the latch. There is a lever on the top that the cable is attached to. it must move to the driver's side to activate the latch. If you can not move the lever, you may be able to unbolt the latch from the core support and open the hood, so that you can activate the lever, and remove the latch from the hood. Cleaning it with brake cleaner, and then dry lubing it and putting it back on the core support. The bolts will leave witness marks on the core support for you to realign the latch.
A sticky latch is not uncommon, so if it is just sticking, clean it, and use some dry lubricant on it once you get it open.
If the cable seems too long to activate the latch, use a fishing split shot to take some of the slack out of the cable, by crimping it around the cable on the passenger's side of the actuating arm.