Jonty's cyst

Going to cheat here, I explained what had happened to Emma of Hazylandboys so I've copied what I said and maybe edit a little!

Whipped Jonty to the vets late afternoon yesterday and they saw him straight away.
A fortnight ago we noticed he had, what we thought was an insect bite on his rear hind quarter. Today there was a black streak in his fur and when I looked it was a real mess. I cleaned him off and there was a hole in his skin, the size of a .22 bullet (That's just an example!). There was also bits around it and in the hole which I thought were eggs of some sort. I squeezed it out, cleaned it up and went to the vets. He said it was a sebaceous cyst which he cleaned with antiseptic, gave him an antibiotic jab, tablets and an antiseptic wash to be used twice a day.
He's ok and it appears to be scabbing quite well but it was quite a hole!