Many years ago, customer was complaining about a click in rear of his new tractor. I went out there and tried to duplicate the noise he was hearing. He said it was from the right rear side. I did many donuts in his yard and no noise. Finally, after several questions I was able to figure out he was hearing the hitch reacting while he was plowing using draft control. Told him to just leave that one lever all the way down and end of problem.
Only reason I bring this up is you said you were moving a round bale. If that hitch settles an inch and corrects it's self you will get a pretty good clunk. One chance in a whole lot that this is your problem but just something to keep in mind as you didn't hear it when pulling the implement.
Most likely wheel but don't overlook front wheel also.