It's a tumour of the connective tissue, destroying bone and thus the reason why some of Bertie's teeth directly under the lump were wobbly.
There is nothing we could have done to prevent it, it's an random thing that occurs apparently and no reason or rhyme why it occurs.
As it is fast growing, it will continue to grow and may advance into his other nostril interfering with his breathing which is something I will need to look out for.
When I asked about how much pain he might be in, it was described as a dull throbbing pain as opposed to a sharp unmanageable pain and signs that the pain has increased is loss of interest in life, reduced interest in eating and sudden weight loss.
Bertie standing guard while Stoney rests
At the moment he is very interested in eating and when I came home today he came trotting over when I entered the paddock and he enjoyed a lovely scratch on his whither. At dinner time he also came trotting up from where he was eating to get his hard feed so he appears to be in good spirits. He has been having fun rolling once or twice a day and enjoying grazing with Stoney his paddock mate. 
Stoney and Bertie enjoying a rest ( risk of lions, tigers and bears at an all time low)
Stoney and Bertie enjoying the sunshine naked.
