It is yours, you won it. Do what you like with it. The guild that raffled it made their raffle money with the quilt, which was their objective, so they have no reason to complain about what happens with the quilt once it is raffled (though don't be surprised if they DO complain - and I would think about that before sharing that info with any guild members).
If getting money for it is your primary objective, then sell it. If you are not concerned about the money, then you have a whole host of other options and there are many fine suggestions here.
You did not seek advice as to what to do with the quilt, just whether or not it would be "bad" to sell it. I say no, it is not bad. It is yours to do with as you please. (and you don't need to pay sales tax on it - you wouldn't do that if you were selling any other used item!)