Firstly I'm not an expert, but I thought I'd give my opinion. It sounds like a hemorrhoid that's possibly thrombosed. If that is the problem, you can buy over the counter creams that help to relieve symptoms and should shrink it. Avoid straining during a bowel movement!
If it's thrombosed, the discomfort should go in a few days, possibly longer, but the lump may remain. The doctor could remove the clot in the surgery and the lump should disappear.
I think I have an external one, but I can only feel it when it swells during a bowel movement, and then shrinks back down within seconds. Other than that, it doesn't bother me at all. No pain or blood. I've noticed, the more I strain, the bigger it gets. I've learned my lesson and I eat loads of fibre and drink loads of water lol.
Hope that helped.