Oh man, that puss! And the video can't show you how it smells. I had a cat that had a lump like that on her back (higher up) and I was looking for a puncture and found a clump of fur with a scab-- when the fur came off and scab came out stuff that looked like that started gushing out and it smelled like rotten milk. The pressure releasing must have been a relief because the cat sighed and started purring. She actually had multiple punctures (the vet missed ALL of them) so I had to trim her fur with scissors and drain the abscess and flush it out for a few weeks. Also had to give her antibiotics. It wasn't pleasant for either of us, but she recovered and was happy.