From what I can decipher, it sounds like the stick damaged the governor mechanism, causing the engine to 'hunt' instead of running at a steady speed. Look at the mechanism carefully to spot any debris stuck in it or bent, missing parts and springs. You'll probably have to get a mechanic to straighten it out.

I agree with 1saxman from your description of the mower surging as soon as you hit the protruding branch , most likely it tweaked either the governor lever or spring assembly . You will have to carefully inspect this mechanizium to see any bent or stretched lever or spring assembly as suggested by Saxman . This accidental damage happens quite often while mowing in close quarters around brush or scrubs etc. Best of luck , let know how you fair .

I had inspected them when I tore apart the carburetor and the rod and spring didn't appear to be bent or stretched. Maybe I will just have to buy new ones to compare and go from there thanks

10-4 Pat !