Small Earnings Exception help

Hello,

I will soon be starting out as a Sole Trader doing some occasional digital work. At this point I am not expecting to make a great deal of money but this could catch me by surprise over the period of a year.

I really don't know whether I should apply for a Small Earnings Exception or not.

If I DO NOT apply and make less than the threshold, how long do I have to claim this back? Is it an easy process?

If I DO APPLY and go over the earning exception, Is this more complex?

Thanks again.

Dan