So I have developed 2 little blisters on my top lip, one on the outside one on the inside. They are yellowish in the middle and about the size of a pin head. Could they be a cold sore? My lips have been dry/sore because my nose is blocked and I breathe through my mouth in my sleep. I also have a bad habit of chewing on my lips Could they be a cold sore? Or just because I've been biting on my lips? The blisters aren't sore now. I've never had a cold sore before so what do I do or how do I know? I'm also pregnant (21 weeks) if I've recently been infected with the cold sore virus (no idea how) will it harm the bubs?