I hate when that happens

I have a cut on the corner of my mouth that I keep ripping open. It started out as a pimple or something and just kept tearing. I thought maybe it was a cold sore but I took cold sore medicine and it didn't make a difference. It starts to heal and I brush my teeth and rip it open. I take a bit of something and rip it open. I forget and yawn and rip it open. It isn't big. It is just like a paper cut in the corner of my mouth. It is driving me nuts.