So this has developed in 24 hours.
My gum split a wee bit - I thought I was brushing too hard with new toothbrush - so I eased off and was more gentle.
Now it's gone bonkers and the wound has just 'grown' all around my tooth. I'm using medicated toothpaste now and swishing my mouth with salt water.
What is going on!? And what can I / should I do that I'm not doing already?