The phrase "big hump" is a casual way of saying that someone has a lot of work or difficulties to overcome. It refers to a significant challenge or obstacle that someone needs to deal with. Full definition
This is quite a flat mixture - it won't rise too much or give a big hump in the middle. (casacostello.com)
We got over the biggest hump quickly when we found that despite Las Vegas is arguably the center of the alcohol (sales) universe, there had NEVER been a Spirits competition here. (fb101.com)
Fortunately, I've already hauled myself over some of the bigger humps when it comes to better health. (fredhutch.org)