a bad taste in (one's)/the mouth

A negative impression (based on something that has already happened). I don't know, man, the fact that he lied to you just leaves a bad taste in my mouth. The way they conducted the interview left a bad taste in my mouth. I don't think I'd accept the job even if they offered it. This kid's been expelled from schools before? Well, that leaves a bad taste in the mouth—why should we accept him?

a bad (or bitter or nasty) taste in the (or someone's) mouth

a strong feeling of distress or disgust following an experience. informal