Something that is bothersome or annoying can be called a hassle. It's a huge hassle to go back to the grocery store after unloading fifteen bags and realizing you forgot milk.
The noun hassle can also refer to an argument or a scuffle. If you get into a hassle at school, you're likely to be called into the principal's office. As a verb, hassle means to annoy or harass repeatedly or chronically. If a bully is constantly hassling you, you should report them.