Personally I would not worry. I know it's difficult not being able to come out and say these things when you feel ready to and instead being forced to discuss it earlier than planned. But it seems to me that the people at your work either haven't reacted or have responded positively to this(?). The truth is people would come to know eventually any way. If everyone is cool with it then if anything this might things easier for you in time as you won't have the anxiety of worrying about if/when to come out to them now. Just be confident and chilled out about it. Don't make a big deal out of it as being gay isn't a big deal
if anyone asks about it just answer calmly but make your response short and to the point.
I highly doubt people will mind. But if anyone does react badly or treat you differently because of it then report it to your boss. You don't deserve to be discriminated against because of your sexuality and your boss should help to protect you from that happening to you whilst at work.
Also, just a thought, are you sure they KNOW you are gay because they saw the post? They may not have realised it was you that posted it. If they can't be sure it was your post and you're really not comfortable with them knowing yet then is there a way you could just tell them it's a site you help out on and that you were just here to give advice? I don't think you should have to pretend to them of course, but if you really don't want them to know, would this be an option?
Good luck.
Honey