ok. Those vertices got "weighted" accidentally in a way you don't wish.
Maybe for automatic asignement upon creation (maybe due to the rest pose you made was not ideal and some mesh limbs were too close) maybe as you made asignments before and they still affect.
1) select the the mesh, the object I mean.
2) hit TAB key. (so to enter in edit (vertices) mode)
3) hit "B" .Now you can quad select. (click and drag to maque a selection) This is the "unnaccurate" way to select in Blender. I prefer hit "B" twice. As now u can "paint select" This is great. As you will see now a circle in the cursor. You can just click and drag as to pait-selecting.Much accurate. remember: to exit the paint-select mode,right click. To deselect, click and drag middle mouse button. To select click and drag left button. To vary the brush size, use mouse wheel. If u don't have a 3 buttons with middle button being also the wheel, then that's your first task.I can't conceive doing 3d, blender or not without it..

(mine is a genius and works like charm in any surface)
3) ok, now you have selected the vertices you want to "unasign". Time to search for the buttons panel. Called "buttons window" .Is essential for u to handle Blender. Go to the EDITING tab, of hit F9.
OK.You now see at left, a drop down that says: "vertex groups".Click on the icon, and chose the bone-group (that's why I told u to set "make groups from closest bones", is easier now to recognize) , like "Bone.003". and hit the button bellow that says "REMOVE" (NOT "DELETE"! as it removes an entire group) as this will remove those vertices from that group influence.With vertices yet selected, do so with any other bone u think is affecting badly.
That's it.
Sorry, further explanation on Blender way of work would take me a life. If you already now a bit of the main interface, this way much should suffice to solve the problem