Boyfriend issues

So my boyfriend and I have been together for over a year. So around a year and a half ago, we decided to go to target because I wanted to go shopping. Well we got there and I was looking around for something cute and I told my boyfriend that I wanted to get a nose piercing I've actually mentioned it a couple times before this. He out of no where said that he cheated! And I was shocked and got hella mad and yelled st him but after that he said that it wasn't true and ever since then I've always been so skeptical about it. Do men or women just say that they cheated only to say that was a lie?