Husband is denying he has a cold sore

So we have a 3 month old baby. And my husband has what looks like to be a cold sore. He is denying it and saying it is a canker sore. It is in the corner of his lips. He gets so defensive when I say don’t kiss our baby. “He’s like it’s not a cold sore” but I’m almost positive it is a cold sore. He is scared I won’t like kiss him or anything. He can be very selfish and he will literally think I don’t want to kiss him! Of course I do but don’t want to spread it! It is making me SO anxious when he doesn’t take it seriously around our baby. If our baby got it it could seriously harm him. What should I say? I just wish he’d understand how serious it could be for our baby! Even if it’s not one! I’m so anxious!!!!