If you get the message "Your Tinder Account is Under Review," it probably means that someone is looking into your account because they think there is something wrong with it.
Tinder might be looking at your profile to make sure you're not a spammer or a fake. Most of the time, this shouldn't be a big deal, but we recommend that you stick to the basics on the app (matching & messaging).
But if you don't think there's anything wrong with your account and don't want to get banned from Tinder completely, you can try contacting customer service (although the jury is out on whether or not this is effective).