You can if you wish but read the "Note" below the list of recently registered players.
To withdraw from member-created tournaments see the Help link on the right side of any tournament page. There is an entry for "How do I withdraw from a tournament". Ignore the part that says "withdrawing from a tournament while you have games in progress will automatically cause you to forfeit all your games on time and negatively affects your timeout % ratio.". Timeout ratio is unaffected.
I have entered the 7th Chess.com Tournament 1201-1400. When I registered, my rating was 1210, but now it is below 1201. I am still registered for the tournament, so how do I delete my name from the registrant list?