Hungry nodes indeed cannot break obsidian or anything similarly hard (not sure if it looks at mining level, hardness, or blast resistance, but it's one of those) or anything behind such a material. Obsidian will not block the gravitational effect, so if you box in the node, it'll still try to suck you in, but it will not break blocks or be able to pull you through the obsidian.
You may not be able to get close enough to the node to place obsidian against it without getting dangerously close. However, you should be able to set up an obsidian wall that the node can pull you up against (but not through), and from there you can set up another such wall closer to the node, and so on and so forth until the node itself is within arm's reach.
Or just grab a personal teleporter of some variety (the EnderIO Staff of Traveling works well), dump your inventory in a chest somewhere, and go for it.