Magic card has clear deformity, options?
Your best option is going to be to buy sleeves for your deck, just make sure that they are completely opaque since with some sleeves you can still see a little bit of the background of the card. Sleeves will not only prevent your card from being considered marked, it will also help protect your deck from getting damaged as much. Some of the most popular brands are Ultra-Pro, KMC, and Dragon Shield.

For your other ideas you can try talking to your local game shop and see if they are willing to exchange it, or Wizards of the Coast customer service, but I wouldn't expect either of them to do anything. For misprint collectors I do not believe this sort of error is the kind they look for, Starcity Games has an article about valuable misprints. As for filling it in yourself, unless you are an amazing artist there is no way you would be able to fill it in without it still being noticable so I wouldn't both trying that.

From the Magic Tournament Rules


  3.11 Marked Cards
  Players are responsible for ensuring that their cards and/or card sleeves are not marked during the course of the
  tournament. A card or sleeve is considered marked if it bears something that makes it possible to identify the card
  without seeing its face, including (but not limited to) scratches, discoloration, and bends.  
  
  If a player’s cards are sleeved, the cards must be examined while in the sleeves to determine if they are marked.