BLISTER UNDER BABYS LIP⚠️‼️

So yesterday I noticed a red dot under my daughters lip (not on the lip but not on the chin) and didn’t think much. Maybe she scratched herself. Well today I looked at it closer and it’s a blister type thing. So I instantly go to my mom because she had a cold sore and was kissing my baby (10 months). I told her that because she kissed her this is what happened. I was for sure that’s the reason why. Butttt then my mom reminded me about how while I was at work the other day and my bf was supposed to be watching her, she was playing around in the toilet.. and normally I wouldn’t be too worried about that but we hadn’t cleaned it in a while because we were out of toilet bowl cleaner and our brush needs to be thrown away but I hadn’t gotten around to it (busy busy momma). What could it be from. We don’t have an diseases but ya never know. What do you think it could be from and what should I do about the blister. Help.