Tax on selling watch?



I’m going to be selling my Pebble 2 HR and going to a Fitbit(not sure which one yet) and was looking for some advice on the sale. I was given the Pebble as a gift some time back so all money from the sale is income to me. Will I be paying tax on this? I’ve heard some nightmare stories about people selling items on eBay and HMRC wanting tax from them so a little worried. According to this salary website I would pay 40% tax on any more income I make. Should I be worrying?

Thanks :slight_smile: