There is no difference between a bump and a lump.
A bump is a lump like, for example, a bump on your skin or a bump in a road.
They have a bump for matting.
Bump Chump Pump Lump
bump, lump, clump, rump, dump, hump
Hump, dump, stump, bump, lump, rump.
Like a hairy lump
It is Knock