An idiom meaning a thorn in one's side — a nuisance or someone (often superior) who obstructs or interferes with you.
彼にとって新しい支店長が目の上のこぶだ。
For him, the new branch manager is a thorn in his side.
あの古い規則が事業の障害になり、目の上のこぶになっている。
That old regulation has become an obstacle to the business — a real nuisance.
社内の派閥が目の上のこぶで、新しい企画が進まない。
Factionalism in the company is a thorn in the side; the new project can't move forward.