You have misunderstood the rules. As you started trading in November last year you don't need to fill out a tax return until the following year. So next January you will be required to fill one out from Dec06-April07 in time for the deadline (which is usually 31st Jan).
So you don't need to worry, you aren't subject to a fine. You do however need to ensure that you register as self-employed within the 3 months of trading.
(Some of this post only applies if you are actually registered as self-employed. I had to change my post slightly as I realised you haven't yet signed up for self-employment, initially I thought you said you had signed on in Dec).
HTH
