If something causes trouble for you, it might be a hassle to deal with the problem. When used as a noun, a hassle is usually a small problem, but if you use the word as a verb, the problem could be large or small.
These sentences use "hassle" as a noun:
Filing the necessary paperwork with the government is a big hassle.
It’s too much of a hassle to drive all the way downtown just to get something to eat. Let’s find a restaurant around here.
Dealing with salespeople can be a hassle.
Going through security at the airport is a hassle.
Why does this have to be such a big hassle?
Going to court to solve a dispute can be a hassle.
These sentences and questions use "hassle" as a verb:
Why are the police hassling those people?
Ron’s parents hassled him about staying out late last night.
Lakeisha’s boss is hassling her at work. He doesn’t like the way she does her job.