picture included Bumper nut access?

[NOsMAN 10 1 Cars]

How do I get to the nut on the side bolts of the rear bumper? It has a rubber ring around it. Tried pulling it of but it won’t budge. Tried searching but everyone mentions angle grinder. Will on use one if I have to. 

[NOsMAN 10 1 Cars]

Look at the state of the nut, no wonder I couldn’t pull of the rubber. The metal ring that inserts into it was completely rusted and expanded. Had to use the angle grinder to cut the bumper instead before gaining access to the bolt.