You can place water inside of it and it will stop the it. You can just relight it. Or use a diamond pick and break the obsidian.
oh, you also might be able to help me with another problem i'm having. are you using a dark room grinder?
hence why obsidian is used as an anti grief block its alot more annoying to grief something made out of obsidian! I was thinking about making a public grinder, and i thought about making it out of obsidian haha. But the idea of misplacing a block scares me...
That would be so cool! If your worried about miss placing obsidian try get an eff 4 or 5 pickaxe, it take a couple of seconds to mine one block!