Hi Rylee, you may get some mixed opinions in response to your question. Some might say that polishing "destroys" the value and collect-ability, while others might say that it improves aesthetics because at least you can see what's going on inside and enjoy the marble's pattern.
I'm assuming you mean a handmade marble that has a fair amount of clear glass encasing the inside pattern. Polishing a marble removes glass and depending on the depth of the damage/dullness a fair amount of glass may need to be removed.
Removing a lot of glass can sometimes expose the "ends" of the inner pattern at each pontil which bugs some people including me, but it's a quick way to tell if a handmade has been polished.
Here are a couple before/after pictures of ~1 5/8" for examples sake **results may vary** lol please excuse the quality if I can get the pics to work. Good luck with your marble what ever you decide to do with it!
I'll also add that chips/dings can add a lot of character to these old marbles. Think of the stories that could be told of games on the playground 100 years ago! I think that's pretty cool in itself.