first- I'm fairly sure this is the wrong place to post that question, ask a mod where to put it.
second-it depends mostly on what type of volcano it is and how big the bomb is (we have anywhere from 10 kilotons to 200 megatons, so that's a very big range. the most likely result is that it would do little to nothing, if it even went off.
Sorry, i forgot to mention how powerful the bomb is. Let us say a B-52 bomber drop a 200 megatons bomb in the Icelandic volcano that has recently erupted. What will happen? is the volcano going to be pulverised and created secondary effect such as lava spilling everywhere and make matter things worse?