From Longman Dictionary of Contemporary Englishstick/stand out like a sore thumbstick/stand out like a sore thumbinformal if someone or something sticks out like a sore thumb, they are very noticeable because they are different from everyone or everything else You stick out like a sore thumb in that uniform. → sore
Examples from the Corpus
stick/stand out like a sore thumb• You can't come to the restaurant dressed in jeans. You'd stick out like a sore thumb.• For these reasons feminist values stand out like a sore thumb.• Having a whole batch together should make an odd one stick out like a sore thumb.• Having said that, in some of the bits of Shoreditch I passed through I stuck out like a sore thumb.• I mean, it sticks out like a sore thumb.• There's no cover, and - as happened to me - any stranger sticks out like a sore thumb.• We stand out like sore thumbs.• You stick out like a sore thumb in that ghastly uniform, Charles. 