Strange lump from bunny's skin

Need a little help - won't be able to get to vet until Monday.

I have a 13 year old bun who developed a small loose cyst under his skin on his left rib cage. Didn't seem to bother him at all. I had a vet tech friend look at it and she thought it's probably a fatty cyst. Since it didn't bother him and wasn't getting bigger, we decided to wait to take him to vet. Closest rabbit savvy one is two hours away and the ride stresses him out. It's probably been four months or so.

Tonight while he's sitting on the couch with me, I noticed some weird thing under his fur. It's the lump! It worked through his skin. Bleh! It moved as I looked so I played kept working it and it popped out. Like a flybot. It's hard, white and brown colored, and smaller than a penny. There is a small hole in his side but he isn't bothered by it.

I'm including pictures. Any ideas? I'm so glad he's fine. Thanks for your help!

It looks like a sebaceous cyst or something from the pictures- but it's very hard to tell without actually seeing it. I'd still bring him to the vet when you get a chance- that wound may need to be cleaned out a bit! Let us know how it goes!