bump (up) against (someone or something)
To touch or strike something or someone, usually lightly and unintentionally. Whenever someone opens the door, it bumps against the coat rack. I lost my balance and bumped up against the person in front of me in line.
bump (up) against someone or something
to strike someone or something accidentally, usually relatively gently. The car bumped up against the curb. The door has bumped against the wall and scratched the paint.